Group Non-negative Matrix Factorization with Natural Categories for Question Retrieval in Community Question Answer Archives Guangyou Zhou author Yubo Chen author Daojian Zeng author Jun Zhao author 2014-08 text Proceedings of COLING 2014, the 25th International Conference on Computational Linguistics: Technical Papers Junichi Tsujii editor Jan Hajic editor Dublin City University and Association for Computational Linguistics Dublin, Ireland conference publication zhou-etal-2014-group https://aclanthology.org/C14-1010/ 2014-08 89 98