 Variational methods for the solution of problems of equilibrium and vibrations by Richard Courant

Bulletin of the American Mathematical Society 49(1), 1–23. Primary PDF: www.ams.org/bull/1943-49-01/S0002-9904-1943-07818-4/S0002-9904-1943-07818-4.pdf . Cited for variational approximation by finite-parameter trial functions, including piecewise-linear constructions; no claim that Courant alone originated every finite-element method. Direct PDF access returned 403.