In natural language understanding, there is a hierarchy of lenses through which we can extract meaning - from words to sentences to paragraphs to documents. At the document level, one of the most useful ways to understand text is by analyzing its topics.
S. Wang, J. Tang, C. Aggarwal, and H. Liu. Proceedings of the 25th ACM International on Conference on Information and Knowledge Management, ACM, (October 2016)
M. Artetxe, G. Labaka, I. Lopez-Gazpio, and E. Agirre. Proceedings of the 22nd Conference on Computational Natural Language Learning, page 282--291. Association for Computational Linguistics, (2018)