UnitedQA: A Hybrid Approach for Open Domain Question Answering Hao Cheng author Yelong Shen author Xiaodong Liu author Pengcheng He author Weizhu Chen author Jianfeng Gao author 2021-08 text Proceedings of the 59th Annual Meeting of the Association for Computational Linguistics and the 11th International Joint Conference on Natural Language Processing (Volume 1: Long Papers) Chengqing Zong editor Fei Xia editor Wenjie Li editor Roberto Navigli editor Association for Computational Linguistics Online conference publication cheng-etal-2021-unitedqa 10.18653/v1/2021.acl-long.240 https://aclanthology.org/2021.acl-long.240/ 2021-08 3080 3090