エルブラン化
Skolem, T. "Logico-combinatorial investigations in the satisfiability or provability of mathematical propositions: A simplified proof of a theorem by L. Löwenheim and generalizations of the theorem". (In van Heijenoort 1967, 252-63.)
Herbrand, J. "Investigations in proof theory: The properties of true propositions". (In van Heijenoort 1967, 525-81.)
van Heijenoort, J. From Frege to Gödel: A Source Book in Mathematical Logic, 1879-1931. Harvard University Press, 1967.