@ARTICLE{BorHol_j2000_a, author = "Henning~Bordihn and Markus~Holzer", title = "Grammar systems with negated conditions in their cooperation protocols", journal = jucs, year = 2000, volume = "6", number = "12", pages = "1165--1184", url = {http://www.jucs.org/jucs_6_12/grammar_systems_with_negated/Bordihn_H.pdf} }