Krzysztof R. Apt Andrea Schaerf The Alma Project, or How First-Order Logic Can Help Us in Imperative Programming. 89-113 http://link.springer.de/link/service/series/0558/bibs/1710/17100089.htm 1999 conf/birthday/1999langmaack Correct System Design db/conf/birthday/langmaack1999.html#AptS99