Fundamental Concepts in Programming Languages Alive
Strachey's Copenhagen lectures — L-values and R-values, first-class functions, parametric vs ad-hoc polymorphism — the vocabulary the field still argues in. Circulated for decades, published in 2000.
Delivered at a NATO summer school in Copenhagen in August 1967, the lecture notes circulated as a cult samizdat for three decades before formal publication in Higher-Order and Symbolic Computation in 2000. They are the source of 'L-value' and 'R-value,' 'first-class' functions, and the parametric/ad-hoc polymorphism distinction.
Strachey wrote CPL — the language so large only a toy implementation existed — to embody these ideas. His taxonomy is the vocabulary of every serious language discussion since; the lecture's influence vastly exceeds its citation count because it was absorbed, not cited.