Splittability of Bilexical Context-Free Grammars is Undecidable Mark-Jan Nederhof author Giorgio Satta author 2011-12 text journal article Computational Linguistics continuing MIT Press Cambridge, MA periodical academic journal nederhof-satta-2011-splittability 10.1162/COLI_a_00079 https://aclanthology.org/J11-4009/ 2011-12 37 4 867 879