Equivalence of the Gries and Martin Proof Rules for Procedure Calls. - A. Bijlsma 001; J. G. Wiltink; P. A. Matthews (Acta Informatica, 1986)

Two Most Nondeterministic Programs. - J. G. Wiltink (Sci. Comput. Program., 1986)

A Deficiency of Natural Deduction. - J. G. Wiltink (Inf. Process. Lett., 1987)

A Sharp Proof Rule for Procedures in wp Semantics. - A. Bijlsma 001; P. A. Matthews; J. G. Wiltink (Acta Informatica, 1989)