Sparse Non-negative Matrix Language Modeling Joris Pelemans author Noam Shazeer author Ciprian Chelba author 2016 text journal article Transactions of the Association for Computational Linguistics continuing MIT Press Cambridge, MA periodical academic journal pelemans-etal-2016-sparse 10.1162/tacl_a_00102 https://aclanthology.org/Q16-1024/ 2016 4 329 342