Empirical Risk Minimization for Probabilistic Grammars: Sample Complexity and Hardness of Learning Shay B Cohen author Noah A Smith author 2012-septemer text journal article Computational Linguistics continuing MIT Press Cambridge, MA periodical academic journal cohen-smith-2012-empirical 10.1162/COLI_a_00092 https://aclanthology.org/J12-3003/ 2012-septemer 38 3 479 526