Robert E. Shostak:
On the Role of Unification in Mechanical Theorem Proving.
319-323
Peter E. Lauer, Roy H. Campbell:
Addenda and Corrigenda: Formal Semantics of a Class of High-Level Primitives for Coordinating Concurrent Processes.
325, (see: Acta Informatika 5: 297-332 (1975))