diff --git a/examples/aishell/asr1/README.md b/examples/aishell/asr1/README.md
index 25b28ede8..a7390fd68 100644
--- a/examples/aishell/asr1/README.md
+++ b/examples/aishell/asr1/README.md
@@ -1,5 +1,5 @@
 # Transformer/Conformer ASR with Aishell
-This example contains code used to train a Transformer or [Conformer](http://arxiv.org/abs/2008.03802) model with [Aishell dataset](http://www.openslr.org/resources/33)
+This example contains code used to train a [u2](https://arxiv.org/pdf/2012.05481.pdf) model (Transformer or [Conformer](https://arxiv.org/pdf/2005.08100.pdf) model) with [Aishell dataset](http://www.openslr.org/resources/33)
 ## Overview
 All the scripts you need are in `run.sh`. There are several stages in `run.sh`, and each stage has its function.
 | Stage | Function                                                     |
diff --git a/examples/librispeech/asr1/README.md b/examples/librispeech/asr1/README.md
index ae252a58b..ca0081444 100644
--- a/examples/librispeech/asr1/README.md
+++ b/examples/librispeech/asr1/README.md
@@ -1,5 +1,5 @@
 # Transformer/Conformer ASR with Librispeech
-This example contains code used to train a Transformer or [Conformer](http://arxiv.org/abs/2008.03802) model with [Librispeech dataset](http://www.openslr.org/resources/12)
+This example contains code used to train [u2](https://arxiv.org/pdf/2012.05481.pdf) model (Transformer or [Conformer](https://arxiv.org/pdf/2005.08100.pdf) model) with [Librispeech dataset](http://www.openslr.org/resources/12)
 ## Overview
 All the scripts you need are in `run.sh`. There are several stages in `run.sh`, and each stage has its function.
 | Stage | Function                                                     |
diff --git a/examples/librispeech/asr2/README.md b/examples/librispeech/asr2/README.md
index 5bc7185a9..26978520d 100644
--- a/examples/librispeech/asr2/README.md
+++ b/examples/librispeech/asr2/README.md
@@ -1,6 +1,6 @@
 # Transformer/Conformer ASR with Librispeech ASR2
 
-This example contains code used to train a Transformer or [Conformer](http://arxiv.org/abs/2008.03802) model with [Librispeech dataset](http://www.openslr.org/resources/12) and use some functions in kaldi.
+This example contains code used to train a [u2](https://arxiv.org/pdf/2012.05481.pdf) model (Transformer or [Conformer](https://arxiv.org/pdf/2005.08100.pdf) model) with [Librispeech dataset](http://www.openslr.org/resources/12) and use some functions in kaldi.
 
 To use this example, you need to install Kaldi first.
 
diff --git a/examples/tiny/asr1/README.md b/examples/tiny/asr1/README.md
index 6a4999aa6..cfa266704 100644
--- a/examples/tiny/asr1/README.md
+++ b/examples/tiny/asr1/README.md
@@ -1,5 +1,5 @@
 # Transformer/Conformer ASR with Tiny
-This example contains code used to train a Transformer or [Conformer](http://arxiv.org/abs/2008.03802) model  Tiny dataset(a part of [[Librispeech dataset](http://www.openslr.org/resources/12)](http://www.openslr.org/resources/33))
+This example contains code used to train a [u2](https://arxiv.org/pdf/2012.05481.pdf) model (Transformer or [Conformer](https://arxiv.org/pdf/2005.08100.pdf) model) with Tiny dataset(a part of [[Librispeech dataset](http://www.openslr.org/resources/12)](http://www.openslr.org/resources/33))
 ## Overview
 All the scripts you need are in `run.sh`. There are several stages in `run.sh`, and each stage has its function.
 | Stage | Function                                                     |