Parsing with Traces: An O(n4) Algorithm and a Structural Representation Jonathan K Kummerfeld author Dan Klein author 2017 text journal article Transactions of the Association for Computational Linguistics continuing MIT Press Cambridge, MA periodical academic journal kummerfeld-klein-2017-parsing 10.1162/tacl_a_00072 https://aclanthology.org/Q17-1031/ 2017 5 441 454