Hearn, Anthony C. "The Problem of Substitution"

Tobey (ed) (1969) Tobey, R. G. (ed) Proceedings of the 1968 Summer Institute on Symbolic Mathematical Computation, IBM Federal Systems Center, Gaithersburg, Maryland, July-August 1968, IBM Programming Laboratory Report No. FSC-69-0312 (proceedings published June 1969).  

Languages mentioned REDUCE {1963}