@InCollection{TALN-2014-Bec-Casadio,
 author       = {Denis B\'echet},
 title        = {{NP}-Completeness of Grammars Based upon Products of Free Pregroups},
 booktitle    = {Categories and Types in Logic, Language, and Physics,
                 Essays Dedicated to Jim Lambek on the Occasion of His 90th Birthday},
 editor       = {Claudia Casadio and Bob Coecke and Michael Moortgat and Philip Scott},
 series       = {Lecture Notes in Computer Science (LNCS)},
 volume       = {8222},
 publisher    = {Springer-Verlag},
 pages        = {51--62},
 ISBN         = {978-3-642-54788-1},
 DOI          = {10.1007/978-3-642-54789-8\_4},
 year         = 2014
}