Using an Extended PROLOG to Solve the Lion and Unicorn Puzzle. - Richard Schmid; Hans-Albert Schneider; Thomas Filkorn (J. Autom. Reason., 1989)

Symbolic Constraint Handling Through Unification in Finite Algebras. - Wolfram Büttner; Klaus Estenfeld; Richard Schmid; Hans-Albert Schneider; Erik Tidén (Appl. Algebra Eng. Commun. Comput., 1990)

Experiences from a Large Industrial Circuit Design Application. - Thomas Filkorn; Richard Schmid; Erik Tidén; Peter Warkentin (ISLP, 1991)