diff --git a/transformer/README.md b/transformer/README.md
index 7cb48b0..1692640 100644
--- a/transformer/README.md
+++ b/transformer/README.md
@@ -1,17 +1,79 @@
-To implement a correct **Transformer Encoder-Decoder** model, we can refer to two resources:
+To implement a correct **Transformer Encoder-Decoder** model, we can refer to some resources:
 
-+ [Pytorch Implementation](https://pytorch.org/docs/stable/_modules/torch/nn/modules/transformer.html#Transformer)
-+ [HuggingFace Implementation: BART (highly recommended)](https://github.com/huggingface/transformers/blob/master/src/transformers/models/bart/modeling_bart.py#L846)
-  + [BartModel](https://github.com/huggingface/transformers/blob/e57468b8a85bad5cc17efbfcfdd3eecb9b8a62ec/src/transformers/models/bart/modeling_bart.py#L1123)
-  + [BartEncoder](https://github.com/huggingface/transformers/blob/e57468b8a85bad5cc17efbfcfdd3eecb9b8a62ec/src/transformers/models/bart/modeling_bart.py#L671)
-  + [BartDecoder](https://github.com/huggingface/transformers/blob/e57468b8a85bad5cc17efbfcfdd3eecb9b8a62ec/src/transformers/models/bart/modeling_bart.py#L846)
-  + [BartLearnedPositionalEmbedding](https://github.com/huggingface/transformers/blob/e57468b8a85bad5cc17efbfcfdd3eecb9b8a62ec/src/transformers/models/bart/modeling_bart.py#L107)
-  + [BartAttention](https://github.com/huggingface/transformers/blob/e57468b8a85bad5cc17efbfcfdd3eecb9b8a62ec/src/transformers/models/bart/modeling_bart.py#L127)
+0. Transformer paper: [Attention Is All You Need](https://arxiv.org/abs/1706.03762)
+1. [Pytorch Implementation](https://pytorch.org/docs/stable/_modules/torch/nn/modules/transformer.html#Transformer)
+2. HuggingFace Implementation: [BERT](https://github.com/huggingface/transformers/tree/master/src/transformers/models/bert) for Encoder & [BART](https://github.com/huggingface/transformers/tree/master/src/transformers/models/bart) for Enc-Dec
 
+In this project, we give the basic definition of the Transformer network (specifying the required classes and the calling logic between them).
+**You can freely modify the definition with knowledge of the context.**
+To build a generic Transformer we need to implement the following classes:
++ [XformerEncoder](https://github.com/AntNLP/fm-gym/blob/b9b0fee45616a52578c1e599073568e11b058f14/transformer/xformer_encoder.py#L5)
++ [XformerDecoder](https://github.com/AntNLP/fm-gym/blob/b9b0fee45616a52578c1e599073568e11b058f14/transformer/xformer_decoder.py#L5)
++ [SelfAttentionSublayer](https://github.com/AntNLP/fm-gym/blob/b9b0fee45616a52578c1e599073568e11b058f14/transformer/attention.py#L31)
++ [CrossAttentionSublayer](https://github.com/AntNLP/fm-gym/blob/b9b0fee45616a52578c1e599073568e11b058f14/transformer/attention.py#L59)
++ [MultiHeadAttention](https://github.com/AntNLP/fm-gym/blob/b9b0fee45616a52578c1e599073568e11b058f14/transformer/attention.py#L5)
++ [FeedforwardSublayer](https://github.com/AntNLP/fm-gym/blob/b9b0fee45616a52578c1e599073568e11b058f14/transformer/feedforward.py#L4)
++ [SinusoidalEmbeddings](https://github.com/AntNLP/fm-gym/blob/b9b0fee45616a52578c1e599073568e11b058f14/transformer/embeddings.py#L4)
++ [LearnableEmbeddings](https://github.com/AntNLP/fm-gym/blob/b9b0fee45616a52578c1e599073568e11b058f14/transformer/embeddings.py#L20)
 
+The tree logic between classes is as follows:
+```
+├── XformerEncoder
+│   ├── SelfAttentionSublayer
+│   │   ├── MultiHeadAttention
+│   ├── FeedforwardSublayer
+├── XformerDecoder
+│   ├── SelfAttentionSublayer
+│   │   ├── MultiHeadAttention
+│   ├── CrossAttentionSublayer
+│   │   ├── MultiHeadAttention
+│   ├── FeedforwardSublayer
+├── LearnableEmbeddings  
+├── SinusoidalEmbeddings
+```
+To obtain the output of a reproduced Transformer, we can define a randomly initialized BERT (Encoder) or BART (Enc-Dec).
+Take BERT as an example:
+```
+├── BertModel
+│   ├── BERTEmbeddings
+│   │   ├── LearnableEmbeddings
+│   │   └── SinusoidalEmbeddings
+│   ├── XformerEncoder
+│   │   ├── SelfAttentionSublayer
+│   │   │   ├── MultiHeadAttention
+│   │   ├── FeedforwardSublayer
+│   ├── BERTMLMHead
+│   ├── BERTNSPHead
+```
+```python
+# Step 1: Set the Random Seed in the program entry 
+# earlier is better
+random.seed(SEED)
+np.random.seed(SEED)
+torch.manual_seed(SEED)
+torch.cuda.manual_seed(SEED)
+
+# Step 2: Load BERT hyperparameters
+from transformers import AutoTokenizer, AutoConfig
+config = AutoConfig.from_pretrained(os.environ['TRANSFORMERS_CACHE']+'bert-base')   # 'bart-base'
+
+# Step 3: Define our BERT
+from bert_model import BertModel
+our_bert = BertModel(
+    vocab_size = config.vocab_size,
+    hidden_size = config.hidden_size,
+    ...
+    ...
+)
+
+# Step 4: Get the model output without dropout
+our_bert.eval()
+inputs = tokenizer("Hello, my dog is cute", return_tensors="pt")
+last_hidden_states, _, _ = our_bert(**inputs)
+```
 
 By referring to the hugging face implementation, we could confirm that we have implemented the **Transformer Encoder-Decoder** model correctly.
-Check that our output is consistent with the Bart output ( `last_hidden_states` in the code below).
+Check that our output is consistent with the BERT/BART output ( `last_hidden_states` in the code below).
 
 ```python
 # Step 1: Set the Random Seed in the program entry 
@@ -24,9 +86,9 @@ torch.cuda.manual_seed(SEED)
 # Step 2: Define a randomly initialized BART model
 from transformers import AutoTokenizer, AutoConfig, AutoModel
 
-config = AutoConfig.from_pretrained(os.environ['TRANSFORMERS_CACHE']+'bart-base')
+config = AutoConfig.from_pretrained(os.environ['TRANSFORMERS_CACHE']+'bert-base')   # 'bart-base'
 model = AutoModel.from_config(config)
-tokenizer = AutoTokenizer.from_pretrained(os.environ['TRANSFORMERS_CACHE']+'bart-base')
+tokenizer = AutoTokenizer.from_pretrained(os.environ['TRANSFORMERS_CACHE']+'bert-base')  # 'bart-base'
 
 # Step 3: Get the model output without dropout
 model.eval()