Perspectives of System Informatics 4th International Andrei Ershov Memorial Conference, PSI 2001, Akademgorodok, Novosibirsk, Russia, July 2-6, 2001, Revised Papers - Bjørner, Dines; Bjørner, Dines; Broy, Manfred; Broy, Manfred; Zamulin, Alexandre; Zamulin, Alexandre (Springer Berlin Heidelberg : Imprint: Springer, 2001)