HiURE: Hierarchical Exemplar Contrastive Learning for Unsupervised Relation Extraction Shuliang Liu author Xuming Hu author Chenwei Zhang author Shu’ang Li author Lijie Wen author Philip Yu author 2022-07 text Proceedings of the 2022 Conference of the North American Chapter of the Association for Computational Linguistics: Human Language Technologies Marine Carpuat editor Marie-Catherine de Marneffe editor Ivan Vladimir Meza Ruiz editor Association for Computational Linguistics Seattle, United States conference publication liu-etal-2022-hiure 10.18653/v1/2022.naacl-main.437 https://aclanthology.org/2022.naacl-main.437/ 2022-07 5970 5980