Harold Abelson and Gerald Jay Sussman, Structure and Interpretation of Computer Programs, 2nd edition, section 1.3.4 footnote 64Archived 2015-03-09 at the Wayback Machine
Christopher Strachey, "Fundamental Concepts in Programming Languages" in Higher-Order and Symbolic Computation13:11 (2000); though published in 2000, these are notes from lectures Strachey delivered in August, 1967
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Harold Abelson and Gerald Jay Sussman, Structure and Interpretation of Computer Programs, 2nd edition, section 1.3.4 footnote 64Archived 2015-03-09 at the Wayback Machine