diff --git a/paddlespeech/s2t/decoders/README.md b/paddlespeech/s2t/decoders/README.md
index ee7d53dea..0b91ddd1b 100644
--- a/paddlespeech/s2t/decoders/README.md
+++ b/paddlespeech/s2t/decoders/README.md
@@ -1,4 +1,5 @@
 # Decoders
+we borrow a lot of code from Espnet Apache 2.0  (http://www.apache.org/licenses/LICENSE-2.0)
 
 ## Reference
 ### CTC Prefix Beam Search
diff --git a/paddlespeech/s2t/decoders/beam_search/batch_beam_search.py b/paddlespeech/s2t/decoders/beam_search/batch_beam_search.py
index 3fc1c435f..ed9790cdf 100644
--- a/paddlespeech/s2t/decoders/beam_search/batch_beam_search.py
+++ b/paddlespeech/s2t/decoders/beam_search/batch_beam_search.py
@@ -11,6 +11,7 @@
 # WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 # See the License for the specific language governing permissions and
 # limitations under the License.
+# Reference espnet Apache 2.0 (http://www.apache.org/licenses/LICENSE-2.0)
 
 
 class BatchBeamSearch():
diff --git a/paddlespeech/s2t/decoders/beam_search/beam_search.py b/paddlespeech/s2t/decoders/beam_search/beam_search.py
index 6c4f069d8..7d79246df 100644
--- a/paddlespeech/s2t/decoders/beam_search/beam_search.py
+++ b/paddlespeech/s2t/decoders/beam_search/beam_search.py
@@ -11,6 +11,7 @@
 # WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 # See the License for the specific language governing permissions and
 # limitations under the License.
+# Reference espnet Apache 2.0 (http://www.apache.org/licenses/LICENSE-2.0)
 """Beam search module."""
 from itertools import chain
 from typing import Any
diff --git a/paddlespeech/s2t/decoders/recog.py b/paddlespeech/s2t/decoders/recog.py
index d0710f9c4..d9324ca02 100644
--- a/paddlespeech/s2t/decoders/recog.py
+++ b/paddlespeech/s2t/decoders/recog.py
@@ -11,6 +11,7 @@
 # WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 # See the License for the specific language governing permissions and
 # limitations under the License.
+# Reference espnet Apache 2.0 (http://www.apache.org/licenses/LICENSE-2.0)
 """V2 backend for `asr_recog.py` using py:class:`decoders.beam_search.BeamSearch`."""
 import jsonlines
 import paddle
diff --git a/paddlespeech/s2t/decoders/recog_bin.py b/paddlespeech/s2t/decoders/recog_bin.py
index e4d81f409..cd7a360ae 100644
--- a/paddlespeech/s2t/decoders/recog_bin.py
+++ b/paddlespeech/s2t/decoders/recog_bin.py
@@ -11,6 +11,7 @@
 # WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 # See the License for the specific language governing permissions and
 # limitations under the License.
+# Reference espnet Apache 2.0 (http://www.apache.org/licenses/LICENSE-2.0)
 """End-to-end speech recognition model decoding script."""
 import logging
 import os
diff --git a/paddlespeech/s2t/decoders/scorers/ctc.py b/paddlespeech/s2t/decoders/scorers/ctc.py
index 74a5f578d..e0ff3d5f9 100644
--- a/paddlespeech/s2t/decoders/scorers/ctc.py
+++ b/paddlespeech/s2t/decoders/scorers/ctc.py
@@ -11,6 +11,7 @@
 # WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 # See the License for the specific language governing permissions and
 # limitations under the License.
+# Reference espnet Apache 2.0 (http://www.apache.org/licenses/LICENSE-2.0)
 """ScorerInterface implementation for CTC."""
 import numpy as np
 import paddle
diff --git a/paddlespeech/s2t/decoders/scorers/length_bonus.py b/paddlespeech/s2t/decoders/scorers/length_bonus.py
index 864e22d17..2e4c84651 100644
--- a/paddlespeech/s2t/decoders/scorers/length_bonus.py
+++ b/paddlespeech/s2t/decoders/scorers/length_bonus.py
@@ -11,6 +11,7 @@
 # WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 # See the License for the specific language governing permissions and
 # limitations under the License.
+# Reference espnet Apache 2.0 (http://www.apache.org/licenses/LICENSE-2.0)
 """Length bonus module."""
 from typing import Any
 from typing import List
diff --git a/paddlespeech/s2t/decoders/scorers/ngram.py b/paddlespeech/s2t/decoders/scorers/ngram.py
index a34d82483..fa8f776af 100644
--- a/paddlespeech/s2t/decoders/scorers/ngram.py
+++ b/paddlespeech/s2t/decoders/scorers/ngram.py
@@ -11,6 +11,7 @@
 # WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 # See the License for the specific language governing permissions and
 # limitations under the License.
+# Reference espnet Apache 2.0 (http://www.apache.org/licenses/LICENSE-2.0)
 """Ngram lm implement."""
 from abc import ABC
 
diff --git a/paddlespeech/s2t/decoders/scorers/scorer_interface.py b/paddlespeech/s2t/decoders/scorers/scorer_interface.py
index 366904a47..ddc780da2 100644
--- a/paddlespeech/s2t/decoders/scorers/scorer_interface.py
+++ b/paddlespeech/s2t/decoders/scorers/scorer_interface.py
@@ -11,6 +11,7 @@
 # WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 # See the License for the specific language governing permissions and
 # limitations under the License.
+# Reference espnet Apache 2.0 (http://www.apache.org/licenses/LICENSE-2.0)
 """Scorer interface module."""
 import warnings
 from typing import Any
diff --git a/paddlespeech/s2t/decoders/utils.py b/paddlespeech/s2t/decoders/utils.py
index 7dff14c11..63709d1a9 100644
--- a/paddlespeech/s2t/decoders/utils.py
+++ b/paddlespeech/s2t/decoders/utils.py
@@ -11,6 +11,7 @@
 # WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 # See the License for the specific language governing permissions and
 # limitations under the License.
+# Reference espnet Apache 2.0 (http://www.apache.org/licenses/LICENSE-2.0)
 import numpy as np
 
 from paddlespeech.s2t.utils.log import Log
diff --git a/paddlespeech/s2t/io/batchfy.py b/paddlespeech/s2t/io/batchfy.py
index 3517f059a..9be37c277 100644
--- a/paddlespeech/s2t/io/batchfy.py
+++ b/paddlespeech/s2t/io/batchfy.py
@@ -11,6 +11,7 @@
 # WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 # See the License for the specific language governing permissions and
 # limitations under the License.
+# Reference espnet Apache 2.0 (http://www.apache.org/licenses/LICENSE-2.0)
 import itertools
 
 import numpy as np
diff --git a/paddlespeech/s2t/io/converter.py b/paddlespeech/s2t/io/converter.py
index 94634360c..aacbad980 100644
--- a/paddlespeech/s2t/io/converter.py
+++ b/paddlespeech/s2t/io/converter.py
@@ -11,6 +11,7 @@
 # WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 # See the License for the specific language governing permissions and
 # limitations under the License.
+# Reference espnet Apache 2.0 (http://www.apache.org/licenses/LICENSE-2.0)
 import numpy as np
 
 from paddlespeech.s2t.io.utility import pad_list
diff --git a/paddlespeech/s2t/io/dataset.py b/paddlespeech/s2t/io/dataset.py
index 121410c8b..4aff9fb2e 100644
--- a/paddlespeech/s2t/io/dataset.py
+++ b/paddlespeech/s2t/io/dataset.py
@@ -11,6 +11,8 @@
 # WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 # See the License for the specific language governing permissions and
 # limitations under the License.
+# Reference espnet Apache 2.0 (http://www.apache.org/licenses/LICENSE-2.0)
+# Reference wenet Apache 2.0 (http://www.apache.org/licenses/LICENSE-2.0)
 from typing import Optional
 
 from paddle.io import Dataset
diff --git a/paddlespeech/s2t/io/reader.py b/paddlespeech/s2t/io/reader.py
index faf2f600b..1e32e620c 100644
--- a/paddlespeech/s2t/io/reader.py
+++ b/paddlespeech/s2t/io/reader.py
@@ -11,6 +11,7 @@
 # WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 # See the License for the specific language governing permissions and
 # limitations under the License.
+# Reference espnet Apache 2.0 (http://www.apache.org/licenses/LICENSE-2.0)
 from collections import OrderedDict
 
 import kaldiio
diff --git a/paddlespeech/s2t/models/asr_interface.py b/paddlespeech/s2t/models/asr_interface.py
index ece83e516..76ba3e2cf 100644
--- a/paddlespeech/s2t/models/asr_interface.py
+++ b/paddlespeech/s2t/models/asr_interface.py
@@ -11,6 +11,7 @@
 # WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 # See the License for the specific language governing permissions and
 # limitations under the License.
+# Reference espnet Apache 2.0 (http://www.apache.org/licenses/LICENSE-2.0)
 """ASR Interface module."""
 import argparse
 
diff --git a/paddlespeech/s2t/models/lm/transformer.py b/paddlespeech/s2t/models/lm/transformer.py
index 447f1dbc3..3fadba1a3 100644
--- a/paddlespeech/s2t/models/lm/transformer.py
+++ b/paddlespeech/s2t/models/lm/transformer.py
@@ -11,6 +11,7 @@
 # WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 # See the License for the specific language governing permissions and
 # limitations under the License.
+# Reference espnet Apache 2.0 (http://www.apache.org/licenses/LICENSE-2.0)
 from typing import Any
 from typing import List
 from typing import Tuple
diff --git a/paddlespeech/s2t/models/lm_interface.py b/paddlespeech/s2t/models/lm_interface.py
index 7ae39b351..02df874f1 100644
--- a/paddlespeech/s2t/models/lm_interface.py
+++ b/paddlespeech/s2t/models/lm_interface.py
@@ -11,6 +11,7 @@
 # WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 # See the License for the specific language governing permissions and
 # limitations under the License.
+# Reference espnet Apache 2.0 (http://www.apache.org/licenses/LICENSE-2.0)
 """Language model interface."""
 import argparse
 
diff --git a/paddlespeech/s2t/models/st_interface.py b/paddlespeech/s2t/models/st_interface.py
index 331f1e824..66ba49da5 100644
--- a/paddlespeech/s2t/models/st_interface.py
+++ b/paddlespeech/s2t/models/st_interface.py
@@ -11,6 +11,7 @@
 # WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 # See the License for the specific language governing permissions and
 # limitations under the License.
+# Reference espnet Apache 2.0 (http://www.apache.org/licenses/LICENSE-2.0)
 """ST Interface module."""
 from .asr_interface import ASRInterface
 from paddlespeech.s2t.utils.dynamic_import import dynamic_import
diff --git a/paddlespeech/s2t/modules/attention.py b/paddlespeech/s2t/modules/attention.py
index d5246777c..5cb37ee7f 100644
--- a/paddlespeech/s2t/modules/attention.py
+++ b/paddlespeech/s2t/modules/attention.py
@@ -11,6 +11,7 @@
 # WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 # See the License for the specific language governing permissions and
 # limitations under the License.
+# Reference wenet Apache 2.0 (http://www.apache.org/licenses/LICENSE-2.0)
 """Multi-Head Attention layer definition."""
 import math
 from typing import Optional
diff --git a/paddlespeech/s2t/modules/cmvn.py b/paddlespeech/s2t/modules/cmvn.py
index 9aa938af7..df529c1c4 100644
--- a/paddlespeech/s2t/modules/cmvn.py
+++ b/paddlespeech/s2t/modules/cmvn.py
@@ -11,6 +11,7 @@
 # WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 # See the License for the specific language governing permissions and
 # limitations under the License.
+# Reference wenet Apache 2.0 (http://www.apache.org/licenses/LICENSE-2.0)
 import paddle
 from paddle import nn
 
diff --git a/paddlespeech/s2t/modules/conformer_convolution.py b/paddlespeech/s2t/modules/conformer_convolution.py
index 39b1ee327..b4632d429 100644
--- a/paddlespeech/s2t/modules/conformer_convolution.py
+++ b/paddlespeech/s2t/modules/conformer_convolution.py
@@ -11,6 +11,7 @@
 # WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 # See the License for the specific language governing permissions and
 # limitations under the License.
+# Reference wenet Apache 2.0 (http://www.apache.org/licenses/LICENSE-2.0)
 """ConvolutionModule definition."""
 from typing import Optional
 from typing import Tuple
diff --git a/paddlespeech/s2t/modules/decoder.py b/paddlespeech/s2t/modules/decoder.py
index 7d545f5e8..bd3760c48 100644
--- a/paddlespeech/s2t/modules/decoder.py
+++ b/paddlespeech/s2t/modules/decoder.py
@@ -11,6 +11,7 @@
 # WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 # See the License for the specific language governing permissions and
 # limitations under the License.
+# Reference wenet Apache 2.0 (http://www.apache.org/licenses/LICENSE-2.0)
 """Decoder definition."""
 from typing import Any
 from typing import List
diff --git a/paddlespeech/s2t/modules/decoder_layer.py b/paddlespeech/s2t/modules/decoder_layer.py
index 816bc9f61..62682bfbe 100644
--- a/paddlespeech/s2t/modules/decoder_layer.py
+++ b/paddlespeech/s2t/modules/decoder_layer.py
@@ -11,6 +11,7 @@
 # WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 # See the License for the specific language governing permissions and
 # limitations under the License.
+# Reference wenet Apache 2.0 (http://www.apache.org/licenses/LICENSE-2.0)
 """Decoder self-attention layer definition."""
 from typing import Optional
 from typing import Tuple
diff --git a/paddlespeech/s2t/modules/embedding.py b/paddlespeech/s2t/modules/embedding.py
index 938898c13..2b92aafe6 100644
--- a/paddlespeech/s2t/modules/embedding.py
+++ b/paddlespeech/s2t/modules/embedding.py
@@ -11,6 +11,7 @@
 # WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 # See the License for the specific language governing permissions and
 # limitations under the License.
+# Reference wenet Apache 2.0 (http://www.apache.org/licenses/LICENSE-2.0)
 """Positonal Encoding Module."""
 import math
 from typing import Tuple
diff --git a/paddlespeech/s2t/modules/encoder.py b/paddlespeech/s2t/modules/encoder.py
index 246536dbe..bf9cfeaa6 100644
--- a/paddlespeech/s2t/modules/encoder.py
+++ b/paddlespeech/s2t/modules/encoder.py
@@ -11,6 +11,7 @@
 # WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 # See the License for the specific language governing permissions and
 # limitations under the License.
+# Reference wenet Apache 2.0 (http://www.apache.org/licenses/LICENSE-2.0)
 """Encoder definition."""
 from typing import List
 from typing import Optional
diff --git a/paddlespeech/s2t/modules/encoder_layer.py b/paddlespeech/s2t/modules/encoder_layer.py
index 0525a6147..7cff5442f 100644
--- a/paddlespeech/s2t/modules/encoder_layer.py
+++ b/paddlespeech/s2t/modules/encoder_layer.py
@@ -11,6 +11,7 @@
 # WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 # See the License for the specific language governing permissions and
 # limitations under the License.
+# Reference wenet Apache 2.0 (http://www.apache.org/licenses/LICENSE-2.0)
 """Encoder self-attention layer definition."""
 from typing import Optional
 from typing import Tuple
diff --git a/paddlespeech/s2t/modules/loss.py b/paddlespeech/s2t/modules/loss.py
index 012ef2426..90f941f7a 100644
--- a/paddlespeech/s2t/modules/loss.py
+++ b/paddlespeech/s2t/modules/loss.py
@@ -11,6 +11,7 @@
 # WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 # See the License for the specific language governing permissions and
 # limitations under the License.
+# Reference wenet Apache 2.0 (http://www.apache.org/licenses/LICENSE-2.0)
 import inspect
 
 import paddle
diff --git a/paddlespeech/s2t/modules/mask.py b/paddlespeech/s2t/modules/mask.py
index 5c7886d45..964d5086f 100644
--- a/paddlespeech/s2t/modules/mask.py
+++ b/paddlespeech/s2t/modules/mask.py
@@ -11,6 +11,7 @@
 # WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 # See the License for the specific language governing permissions and
 # limitations under the License.
+# Reference wenet Apache 2.0 (http://www.apache.org/licenses/LICENSE-2.0)
 import paddle
 
 from paddlespeech.s2t.utils.log import Log
diff --git a/paddlespeech/s2t/modules/positionwise_feed_forward.py b/paddlespeech/s2t/modules/positionwise_feed_forward.py
index ccea8e57d..0d9c2e296 100644
--- a/paddlespeech/s2t/modules/positionwise_feed_forward.py
+++ b/paddlespeech/s2t/modules/positionwise_feed_forward.py
@@ -11,6 +11,7 @@
 # WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 # See the License for the specific language governing permissions and
 # limitations under the License.
+# Reference wenet Apache 2.0 (http://www.apache.org/licenses/LICENSE-2.0)
 """Positionwise feed forward layer definition."""
 import paddle
 from paddle import nn
diff --git a/paddlespeech/s2t/modules/subsampling.py b/paddlespeech/s2t/modules/subsampling.py
index 6b8c28c6a..b60a6b1cd 100644
--- a/paddlespeech/s2t/modules/subsampling.py
+++ b/paddlespeech/s2t/modules/subsampling.py
@@ -11,6 +11,7 @@
 # WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 # See the License for the specific language governing permissions and
 # limitations under the License.
+# Reference wenet Apache 2.0 (http://www.apache.org/licenses/LICENSE-2.0)
 """Subsampling layer definition."""
 from typing import Tuple
 
diff --git a/paddlespeech/s2t/training/extensions/evaluator.py b/paddlespeech/s2t/training/extensions/evaluator.py
index 9da0d7316..5989e3135 100644
--- a/paddlespeech/s2t/training/extensions/evaluator.py
+++ b/paddlespeech/s2t/training/extensions/evaluator.py
@@ -11,6 +11,7 @@
 # WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 # See the License for the specific language governing permissions and
 # limitations under the License.
+# Reference chainer MIT (https://opensource.org/licenses/MIT)
 from typing import Dict
 
 import paddle
diff --git a/paddlespeech/s2t/training/extensions/extension.py b/paddlespeech/s2t/training/extensions/extension.py
index 02f924951..1eb034273 100644
--- a/paddlespeech/s2t/training/extensions/extension.py
+++ b/paddlespeech/s2t/training/extensions/extension.py
@@ -11,6 +11,7 @@
 # WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 # See the License for the specific language governing permissions and
 # limitations under the License.
+# Reference chainer MIT (https://opensource.org/licenses/MIT)
 PRIORITY_WRITER = 300
 PRIORITY_EDITOR = 200
 PRIORITY_READER = 100
diff --git a/paddlespeech/s2t/training/extensions/plot.py b/paddlespeech/s2t/training/extensions/plot.py
index 6fbb4d4dc..d2e5e321f 100644
--- a/paddlespeech/s2t/training/extensions/plot.py
+++ b/paddlespeech/s2t/training/extensions/plot.py
@@ -11,6 +11,7 @@
 # WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 # See the License for the specific language governing permissions and
 # limitations under the License.
+# Reference chainer MIT (https://opensource.org/licenses/MIT)
 import copy
 import os
 
diff --git a/paddlespeech/s2t/training/extensions/snapshot.py b/paddlespeech/s2t/training/extensions/snapshot.py
index 753c7ec0e..fb4e80fee 100644
--- a/paddlespeech/s2t/training/extensions/snapshot.py
+++ b/paddlespeech/s2t/training/extensions/snapshot.py
@@ -11,6 +11,7 @@
 # WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 # See the License for the specific language governing permissions and
 # limitations under the License.
+# Reference chainer MIT (https://opensource.org/licenses/MIT)
 import os
 from datetime import datetime
 from pathlib import Path
diff --git a/paddlespeech/s2t/training/optimizer.py b/paddlespeech/s2t/training/optimizer.py
index 8ed30769f..f0bcb313e 100644
--- a/paddlespeech/s2t/training/optimizer.py
+++ b/paddlespeech/s2t/training/optimizer.py
@@ -11,6 +11,7 @@
 # WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 # See the License for the specific language governing permissions and
 # limitations under the License.
+# Reference espnet Apache 2.0 (http://www.apache.org/licenses/LICENSE-2.0)
 from typing import Any
 from typing import Dict
 from typing import Text
diff --git a/paddlespeech/s2t/training/reporter.py b/paddlespeech/s2t/training/reporter.py
index 7afc33f38..22b267521 100644
--- a/paddlespeech/s2t/training/reporter.py
+++ b/paddlespeech/s2t/training/reporter.py
@@ -11,6 +11,7 @@
 # WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 # See the License for the specific language governing permissions and
 # limitations under the License.
+# Reference chainer MIT (https://opensource.org/licenses/MIT)
 import contextlib
 import math
 from collections import defaultdict
diff --git a/paddlespeech/s2t/training/scheduler.py b/paddlespeech/s2t/training/scheduler.py
index f850f6f50..732cbf0b5 100644
--- a/paddlespeech/s2t/training/scheduler.py
+++ b/paddlespeech/s2t/training/scheduler.py
@@ -11,6 +11,7 @@
 # WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 # See the License for the specific language governing permissions and
 # limitations under the License.
+# Reference espnet Apache 2.0 (http://www.apache.org/licenses/LICENSE-2.0)
 from typing import Any
 from typing import Dict
 from typing import Text
diff --git a/paddlespeech/s2t/training/triggers/compare_value_trigger.py b/paddlespeech/s2t/training/triggers/compare_value_trigger.py
index efb928e2c..7c5502681 100644
--- a/paddlespeech/s2t/training/triggers/compare_value_trigger.py
+++ b/paddlespeech/s2t/training/triggers/compare_value_trigger.py
@@ -11,6 +11,7 @@
 # WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 # See the License for the specific language governing permissions and
 # limitations under the License.
+# Reference chainer MIT (https://opensource.org/licenses/MIT)
 from ..reporter import DictSummary
 from .utils import get_trigger
 
diff --git a/paddlespeech/s2t/training/triggers/interval_trigger.py b/paddlespeech/s2t/training/triggers/interval_trigger.py
index 1e04afad8..14201d29c 100644
--- a/paddlespeech/s2t/training/triggers/interval_trigger.py
+++ b/paddlespeech/s2t/training/triggers/interval_trigger.py
@@ -11,6 +11,7 @@
 # WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 # See the License for the specific language governing permissions and
 # limitations under the License.
+# Reference chainer MIT (https://opensource.org/licenses/MIT)
 
 
 class IntervalTrigger():
diff --git a/paddlespeech/s2t/training/triggers/limit_trigger.py b/paddlespeech/s2t/training/triggers/limit_trigger.py
index ecd527ac5..cd96040ef 100644
--- a/paddlespeech/s2t/training/triggers/limit_trigger.py
+++ b/paddlespeech/s2t/training/triggers/limit_trigger.py
@@ -11,6 +11,7 @@
 # WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 # See the License for the specific language governing permissions and
 # limitations under the License.
+# Reference chainer MIT (https://opensource.org/licenses/MIT)
 
 
 class LimitTrigger():
diff --git a/paddlespeech/s2t/training/triggers/time_trigger.py b/paddlespeech/s2t/training/triggers/time_trigger.py
index e31179a9f..53c398d11 100644
--- a/paddlespeech/s2t/training/triggers/time_trigger.py
+++ b/paddlespeech/s2t/training/triggers/time_trigger.py
@@ -11,6 +11,7 @@
 # WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 # See the License for the specific language governing permissions and
 # limitations under the License.
+# Reference chainer MIT (https://opensource.org/licenses/MIT)
 
 
 class TimeTrigger():
diff --git a/paddlespeech/s2t/training/updaters/standard_updater.py b/paddlespeech/s2t/training/updaters/standard_updater.py
index 83180a38d..a686af743 100644
--- a/paddlespeech/s2t/training/updaters/standard_updater.py
+++ b/paddlespeech/s2t/training/updaters/standard_updater.py
@@ -11,6 +11,7 @@
 # WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 # See the License for the specific language governing permissions and
 # limitations under the License.
+# Reference chainer MIT (https://opensource.org/licenses/MIT)
 from typing import Dict
 from typing import Optional
 
diff --git a/paddlespeech/s2t/training/updaters/trainer.py b/paddlespeech/s2t/training/updaters/trainer.py
index dcf844e36..5a1295eb3 100644
--- a/paddlespeech/s2t/training/updaters/trainer.py
+++ b/paddlespeech/s2t/training/updaters/trainer.py
@@ -11,6 +11,7 @@
 # WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 # See the License for the specific language governing permissions and
 # limitations under the License.
+# Reference chainer MIT (https://opensource.org/licenses/MIT)
 import sys
 import traceback
 from collections import OrderedDict
diff --git a/paddlespeech/s2t/training/updaters/updater.py b/paddlespeech/s2t/training/updaters/updater.py
index ff8d925ff..427722d2f 100644
--- a/paddlespeech/s2t/training/updaters/updater.py
+++ b/paddlespeech/s2t/training/updaters/updater.py
@@ -11,6 +11,7 @@
 # WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 # See the License for the specific language governing permissions and
 # limitations under the License.
+# Reference chainer MIT (https://opensource.org/licenses/MIT)
 from dataclasses import dataclass
 
 import paddle
diff --git a/paddlespeech/s2t/transform/add_deltas.py b/paddlespeech/s2t/transform/add_deltas.py
index 4cab0084e..0a2f34198 100644
--- a/paddlespeech/s2t/transform/add_deltas.py
+++ b/paddlespeech/s2t/transform/add_deltas.py
@@ -11,6 +11,7 @@
 # WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 # See the License for the specific language governing permissions and
 # limitations under the License.
+# Reference espnet Apache 2.0 (http://www.apache.org/licenses/LICENSE-2.0)
 import numpy as np
 
 
diff --git a/paddlespeech/s2t/transform/channel_selector.py b/paddlespeech/s2t/transform/channel_selector.py
index d985b482d..bc8a14bf0 100644
--- a/paddlespeech/s2t/transform/channel_selector.py
+++ b/paddlespeech/s2t/transform/channel_selector.py
@@ -11,6 +11,7 @@
 # WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 # See the License for the specific language governing permissions and
 # limitations under the License.
+# Reference espnet Apache 2.0 (http://www.apache.org/licenses/LICENSE-2.0)
 import numpy
 
 
diff --git a/paddlespeech/s2t/transform/cmvn.py b/paddlespeech/s2t/transform/cmvn.py
index 5d3185906..749d5e187 100644
--- a/paddlespeech/s2t/transform/cmvn.py
+++ b/paddlespeech/s2t/transform/cmvn.py
@@ -11,6 +11,7 @@
 # WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 # See the License for the specific language governing permissions and
 # limitations under the License.
+# Reference espnet Apache 2.0 (http://www.apache.org/licenses/LICENSE-2.0)
 import io
 
 import h5py
diff --git a/paddlespeech/s2t/transform/functional.py b/paddlespeech/s2t/transform/functional.py
index e23d55f9d..afbf4a59f 100644
--- a/paddlespeech/s2t/transform/functional.py
+++ b/paddlespeech/s2t/transform/functional.py
@@ -11,6 +11,7 @@
 # WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 # See the License for the specific language governing permissions and
 # limitations under the License.
+# Reference espnet Apache 2.0 (http://www.apache.org/licenses/LICENSE-2.0)
 import inspect
 
 from paddlespeech.s2t.transform.transform_interface import TransformInterface
diff --git a/paddlespeech/s2t/transform/perturb.py b/paddlespeech/s2t/transform/perturb.py
index f7e8bb764..8671420c1 100644
--- a/paddlespeech/s2t/transform/perturb.py
+++ b/paddlespeech/s2t/transform/perturb.py
@@ -11,6 +11,7 @@
 # WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 # See the License for the specific language governing permissions and
 # limitations under the License.
+# Reference espnet Apache 2.0 (http://www.apache.org/licenses/LICENSE-2.0)
 import librosa
 import numpy
 import scipy
diff --git a/paddlespeech/s2t/transform/spec_augment.py b/paddlespeech/s2t/transform/spec_augment.py
index 01ead8add..76e101848 100644
--- a/paddlespeech/s2t/transform/spec_augment.py
+++ b/paddlespeech/s2t/transform/spec_augment.py
@@ -11,6 +11,7 @@
 # WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 # See the License for the specific language governing permissions and
 # limitations under the License.
+# Reference espnet Apache 2.0 (http://www.apache.org/licenses/LICENSE-2.0)
 """Spec Augment module for preprocessing i.e., data augmentation"""
 import random
 
diff --git a/paddlespeech/s2t/transform/spectrogram.py b/paddlespeech/s2t/transform/spectrogram.py
index e63bd6803..aeedf545b 100644
--- a/paddlespeech/s2t/transform/spectrogram.py
+++ b/paddlespeech/s2t/transform/spectrogram.py
@@ -11,6 +11,7 @@
 # WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 # See the License for the specific language governing permissions and
 # limitations under the License.
+# Reference espnet Apache 2.0 (http://www.apache.org/licenses/LICENSE-2.0)
 import librosa
 import numpy as np
 
diff --git a/paddlespeech/s2t/transform/transform_interface.py b/paddlespeech/s2t/transform/transform_interface.py
index 7ab29554e..a7e04ffcf 100644
--- a/paddlespeech/s2t/transform/transform_interface.py
+++ b/paddlespeech/s2t/transform/transform_interface.py
@@ -11,7 +11,9 @@
 # WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 # See the License for the specific language governing permissions and
 # limitations under the License.
-# TODO(karita): add this to all the transform impl.
+# Reference espnet Apache 2.0 (http://www.apache.org/licenses/LICENSE-2.0)
+
+
 class TransformInterface:
     """Transform Interface"""
 
diff --git a/paddlespeech/s2t/transform/transformation.py b/paddlespeech/s2t/transform/transformation.py
index d9bb7c168..f0d1cd175 100644
--- a/paddlespeech/s2t/transform/transformation.py
+++ b/paddlespeech/s2t/transform/transformation.py
@@ -11,6 +11,7 @@
 # WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 # See the License for the specific language governing permissions and
 # limitations under the License.
+# Reference espnet Apache 2.0 (http://www.apache.org/licenses/LICENSE-2.0)
 """Transformation module."""
 import copy
 import io
@@ -23,8 +24,6 @@ import yaml
 
 from paddlespeech.s2t.utils.dynamic_import import dynamic_import
 
-# TODO(karita): inherit TransformInterface
-# TODO(karita): register cmd arguments in asr_train.py
 import_alias = dict(
     identity="paddlespeech.s2t.transform.transform_interface:Identity",
     time_warp="paddlespeech.s2t.transform.spec_augment:TimeWarp",
diff --git a/paddlespeech/s2t/transform/wpe.py b/paddlespeech/s2t/transform/wpe.py
index d82005f64..463810dda 100644
--- a/paddlespeech/s2t/transform/wpe.py
+++ b/paddlespeech/s2t/transform/wpe.py
@@ -11,6 +11,7 @@
 # WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 # See the License for the specific language governing permissions and
 # limitations under the License.
+# Reference espnet Apache 2.0 (http://www.apache.org/licenses/LICENSE-2.0)
 from nara_wpe.wpe import wpe
 
 
diff --git a/paddlespeech/s2t/utils/asr_utils.py b/paddlespeech/s2t/utils/asr_utils.py
index 6f86e56f7..9184fd6af 100644
--- a/paddlespeech/s2t/utils/asr_utils.py
+++ b/paddlespeech/s2t/utils/asr_utils.py
@@ -11,6 +11,7 @@
 # WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 # See the License for the specific language governing permissions and
 # limitations under the License.
+# Reference espnet Apache 2.0 (http://www.apache.org/licenses/LICENSE-2.0)
 import json
 
 import numpy as np
@@ -18,7 +19,6 @@ import numpy as np
 __all__ = ["label_smoothing_dist"]
 
 
-# TODO(takaaki-hori): add different smoothing methods
 def label_smoothing_dist(odim, lsm_type, transcript=None, blank=0):
     """Obtain label distribution for loss smoothing.
 
diff --git a/paddlespeech/s2t/utils/check_kwargs.py b/paddlespeech/s2t/utils/check_kwargs.py
index 1ee7329ba..11214aac7 100644
--- a/paddlespeech/s2t/utils/check_kwargs.py
+++ b/paddlespeech/s2t/utils/check_kwargs.py
@@ -11,6 +11,7 @@
 # WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 # See the License for the specific language governing permissions and
 # limitations under the License.
+# Reference espnet Apache 2.0 (http://www.apache.org/licenses/LICENSE-2.0)
 import inspect
 
 
diff --git a/paddlespeech/s2t/utils/cli_readers.py b/paddlespeech/s2t/utils/cli_readers.py
index 010adb7a9..a1742d4f0 100644
--- a/paddlespeech/s2t/utils/cli_readers.py
+++ b/paddlespeech/s2t/utils/cli_readers.py
@@ -11,6 +11,7 @@
 # WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 # See the License for the specific language governing permissions and
 # limitations under the License.
+# Reference espnet Apache 2.0 (http://www.apache.org/licenses/LICENSE-2.0)
 import io
 import logging
 import sys
diff --git a/paddlespeech/s2t/utils/cli_utils.py b/paddlespeech/s2t/utils/cli_utils.py
index f8e1d60bf..8c3953d69 100644
--- a/paddlespeech/s2t/utils/cli_utils.py
+++ b/paddlespeech/s2t/utils/cli_utils.py
@@ -11,6 +11,7 @@
 # WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 # See the License for the specific language governing permissions and
 # limitations under the License.
+# Reference espnet Apache 2.0 (http://www.apache.org/licenses/LICENSE-2.0)
 import sys
 from collections.abc import Sequence
 from distutils.util import strtobool as dist_strtobool
diff --git a/paddlespeech/s2t/utils/cli_writers.py b/paddlespeech/s2t/utils/cli_writers.py
index 5866a82ee..4fa7824e7 100644
--- a/paddlespeech/s2t/utils/cli_writers.py
+++ b/paddlespeech/s2t/utils/cli_writers.py
@@ -11,6 +11,7 @@
 # WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 # See the License for the specific language governing permissions and
 # limitations under the License.
+# Reference espnet Apache 2.0 (http://www.apache.org/licenses/LICENSE-2.0)
 from pathlib import Path
 from typing import Dict
 
diff --git a/paddlespeech/s2t/utils/ctc_utils.py b/paddlespeech/s2t/utils/ctc_utils.py
index ff23350a3..5e5714469 100644
--- a/paddlespeech/s2t/utils/ctc_utils.py
+++ b/paddlespeech/s2t/utils/ctc_utils.py
@@ -11,6 +11,7 @@
 # WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 # See the License for the specific language governing permissions and
 # limitations under the License.
+# Reference wenet Apache 2.0 (http://www.apache.org/licenses/LICENSE-2.0)
 from typing import List
 
 import numpy as np
@@ -138,16 +139,6 @@ def forced_align(ctc_probs: paddle.Tensor, y: paddle.Tensor,
     return output_alignment
 
 
-# ctc_align(
-# self.model,
-# self.align_loader,
-# self.config.decoding.batch_size,
-# self.align_loader.collate_fn.stride_ms,
-# self.align_loader.collate_fn.vocab_list,
-# self.args.result_file,
-# )
-
-
 def ctc_align(model, dataloader, batch_size, stride_ms, token_dict,
               result_file):
     """ctc alignment.
diff --git a/paddlespeech/s2t/utils/dynamic_import.py b/paddlespeech/s2t/utils/dynamic_import.py
index ddf17afe9..9b415bb7f 100644
--- a/paddlespeech/s2t/utils/dynamic_import.py
+++ b/paddlespeech/s2t/utils/dynamic_import.py
@@ -11,6 +11,7 @@
 # WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 # See the License for the specific language governing permissions and
 # limitations under the License.
+# Reference espnet Apache 2.0 (http://www.apache.org/licenses/LICENSE-2.0)
 import importlib
 import inspect
 from typing import Any
diff --git a/paddlespeech/t2s/training/extension.py b/paddlespeech/t2s/training/extension.py
index 07e92696e..cc59e9222 100644
--- a/paddlespeech/t2s/training/extension.py
+++ b/paddlespeech/t2s/training/extension.py
@@ -11,6 +11,7 @@
 # WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 # See the License for the specific language governing permissions and
 # limitations under the License.
+# Reference chainer MIT (https://opensource.org/licenses/MIT)
 from typing import Callable
 
 PRIORITY_WRITER = 300
diff --git a/paddlespeech/t2s/training/extensions/evaluator.py b/paddlespeech/t2s/training/extensions/evaluator.py
index 28249d096..3d17f70cd 100644
--- a/paddlespeech/t2s/training/extensions/evaluator.py
+++ b/paddlespeech/t2s/training/extensions/evaluator.py
@@ -11,6 +11,7 @@
 # WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 # See the License for the specific language governing permissions and
 # limitations under the License.
+# Reference chainer MIT (https://opensource.org/licenses/MIT)
 from typing import Dict
 
 import paddle
diff --git a/paddlespeech/t2s/training/extensions/snapshot.py b/paddlespeech/t2s/training/extensions/snapshot.py
index 2e4015969..f9b672687 100644
--- a/paddlespeech/t2s/training/extensions/snapshot.py
+++ b/paddlespeech/t2s/training/extensions/snapshot.py
@@ -11,6 +11,7 @@
 # WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 # See the License for the specific language governing permissions and
 # limitations under the License.
+# Reference chainer MIT (https://opensource.org/licenses/MIT)
 import logging
 import os
 from datetime import datetime
diff --git a/paddlespeech/t2s/training/reporter.py b/paddlespeech/t2s/training/reporter.py
index 013c754e3..93c1e1776 100644
--- a/paddlespeech/t2s/training/reporter.py
+++ b/paddlespeech/t2s/training/reporter.py
@@ -11,6 +11,7 @@
 # WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 # See the License for the specific language governing permissions and
 # limitations under the License.
+# Reference chainer MIT (https://opensource.org/licenses/MIT)
 import contextlib
 import math
 from collections import defaultdict
diff --git a/paddlespeech/t2s/training/triggers/interval_trigger.py b/paddlespeech/t2s/training/triggers/interval_trigger.py
index 98c036846..a83139ba9 100644
--- a/paddlespeech/t2s/training/triggers/interval_trigger.py
+++ b/paddlespeech/t2s/training/triggers/interval_trigger.py
@@ -11,6 +11,7 @@
 # WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 # See the License for the specific language governing permissions and
 # limitations under the License.
+# Reference chainer MIT (https://opensource.org/licenses/MIT)
 
 
 class IntervalTrigger(object):
diff --git a/paddlespeech/t2s/training/triggers/limit_trigger.py b/paddlespeech/t2s/training/triggers/limit_trigger.py
index dd7a135e0..db1db774e 100644
--- a/paddlespeech/t2s/training/triggers/limit_trigger.py
+++ b/paddlespeech/t2s/training/triggers/limit_trigger.py
@@ -11,6 +11,7 @@
 # WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 # See the License for the specific language governing permissions and
 # limitations under the License.
+# Reference chainer MIT (https://opensource.org/licenses/MIT)
 
 
 class LimitTrigger(object):
diff --git a/paddlespeech/t2s/training/triggers/time_trigger.py b/paddlespeech/t2s/training/triggers/time_trigger.py
index aff938255..d7123524b 100644
--- a/paddlespeech/t2s/training/triggers/time_trigger.py
+++ b/paddlespeech/t2s/training/triggers/time_trigger.py
@@ -11,6 +11,7 @@
 # WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 # See the License for the specific language governing permissions and
 # limitations under the License.
+# Reference chainer MIT (https://opensource.org/licenses/MIT)
 
 
 class TimeTrigger(object):
diff --git a/paddlespeech/t2s/training/updater.py b/paddlespeech/t2s/training/updater.py
index 1db3d5f9e..a7ea9c2d3 100644
--- a/paddlespeech/t2s/training/updater.py
+++ b/paddlespeech/t2s/training/updater.py
@@ -11,6 +11,7 @@
 # WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 # See the License for the specific language governing permissions and
 # limitations under the License.
+# Reference chainer MIT (https://opensource.org/licenses/MIT)
 import logging
 from dataclasses import dataclass
 
diff --git a/paddlespeech/t2s/training/updaters/standard_updater.py b/paddlespeech/t2s/training/updaters/standard_updater.py
index 2d00d196f..ecbe0e6a8 100644
--- a/paddlespeech/t2s/training/updaters/standard_updater.py
+++ b/paddlespeech/t2s/training/updaters/standard_updater.py
@@ -11,6 +11,7 @@
 # WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 # See the License for the specific language governing permissions and
 # limitations under the License.
+# Reference chainer MIT (https://opensource.org/licenses/MIT)
 import logging
 import time
 from typing import Dict