Gazdar, Gerald, Pullum, Geoffrey K., Carpenter, Robert, Hukari, Thomas and Levine, Robert D. 1986. “Category Structures.” csli–87–102. Stanford, California: Center for the Study of Language; Information.
Gazdar, Gerald, Pullum, Geoffrey K., Carpenter, Robert, Hukari, Thomas and Levine, Robert D. 1988. “Category Structures.”Computational Linguistics 14(1): 1–19.