Unsupervised Sparse Vector Densification for Short Text Similarity Yangqiu Song author Dan Roth author 2015-may–jun text Proceedings of the 2015 Conference of the North American Chapter of the Association for Computational Linguistics: Human Language Technologies Rada Mihalcea editor Joyce Chai editor Anoop Sarkar editor Association for Computational Linguistics Denver, Colorado conference publication song-roth-2015-unsupervised 10.3115/v1/N15-1138 https://aclanthology.org/N15-1138/ 2015-may–jun 1275 1280