BERT

DistilBERT, a distilled version of BERT: smaller, faster, cheaper and lighter (2019)

Sentence-BERT: Sentence Embeddings using Siamese BERT-Networks

RoBERTa: A Robustly Optimized BERT Pretraining Approach (2019)

BERT: Pre-training of Deep Bidirectional Transformers for Language Understanding (2018)