1. A Cook's tour of countable nondeterminism;Apt,1981
2. Correctness Preserving Program Refinements: Proof Theory and Applications;Back,1980
3. Semantics of unbounded nondeterminism;Back,1980
4. Proving total correctness of nondeterministic programs in infinitary logic;Back;Acta Inform.,1981
5. Semantics of infinite processes using generalised trees;de Bakker;Mathematical Centre Report IW 82/77,1977