Neural Abstractive Multi-Document Summarization: Hierarchical or Flat Structure? Ye Ma author Lu Zong author 2020-12 text Proceedings of the Second International Workshop of Discourse Processing Qun Liu editor Deyi Xiong editor Shili Ge editor Xiaojun Zhang editor Association for Computational Linguistics Suzhou, China conference publication ma-zong-2020-neural 10.18653/v1/2020.iwdp-1.6 https://aclanthology.org/2020.iwdp-1.6/ 2020-12 29 37