Update README.md

README.md

@@ -61,3 +61,8 @@ with torch.no_grad():
 # bertweet = TFAutoModel.from_pretrained("vinai/bertweet-large")
 ```
 
+### <a name="preprocess"></a> Normalize raw input Tweets 
+
+Before applying BPE to the pre-training corpus of English Tweets, we tokenized these  Tweets using `TweetTokenizer` from the NLTK toolkit and used the `emoji` package to translate emotion icons into text strings (here, each icon is referred to as a word token).   We also normalized the Tweets by converting user mentions and web/url links into special tokens `@USER` and `HTTPURL`, respectively. Thus it is recommended to also apply the same pre-processing step for BERTweet-based downstream applications w.r.t. the raw input Tweets. 
+
+Please find examples of normalizing raw input Tweets at [BERTweet's homepage](https://github.com/VinAIResearch/BERTweet#preprocess)!