McCarthy, John; Abrahams, Paul W.; Edwards, Daniel J.; Hart, Timothy P.; Levin, Michael I. (1985). LISP 1.5 Programmer's Manual. MIT Press. ISBN0-262-13011-4. See in particular p. 12 for functions that search an association list and use it to substitute symbols in another expression, and p. 103 for the application of association lists in maintaining variable bindings.