HIBERT: Document Level Pre-training of Hierarchical Bidirectional Transformers for Document Summarization Xingxing Zhang author Furu Wei author Ming Zhou author 2019-07 text Proceedings of the 57th Annual Meeting of the Association for Computational Linguistics Anna Korhonen editor David Traum editor Lluís Màrquez editor Association for Computational Linguistics Florence, Italy conference publication zhang-etal-2019-hibert 10.18653/v1/P19-1499 https://aclanthology.org/P19-1499/ 2019-07 5059 5069