Timothy A. D. Fowler. Term Graphs and the NP-Completeness of the Product-Free Lambek Calculus. In Philippe de Groote, Markus Egg, Laura Kallmeyer, editors, Formal Grammar - 14th International Conference, FG 2009, Bordeaux, France, July 25-26, 2009, Revised Selected Papers. Volume 5591 of Lecture Notes in Computer Science, pages 150-166, Springer, 2009. [doi]
Abstract is missing.