k-Valued Non-associative Lambek Grammars (Without Product) Form a Strict Hierarchy of Languages.

Denis Béchet Annie Foret k-Valued Non-associative Lambek Grammars (Without Product) Form a Strict Hierarchy of Languages. 1-17 2005 conf/lacl/2005 LACL http://dx.doi.org/10.1007/11422532_1 db/conf/lacl/lacl2005.html#BechetF05