Hilbert's Twenty-Third Problem

This is a list of some references and links related to Hilbert's twenty-third problem.

1996	S. Chern: Remarks on Hilbert's 23rd problem. Math. Intelligencer 18, no. 4, 7-8.
1976	G. Stampacchia: Hilbert's twenty-third problem. Extensions of the calculus of variations. Proceedings of the Symposium in Pure Mathematics of the American Mathematical Society, Held at Northern Illinois University 1974, (edited by F.E.Browder), 611-628.
1900	D. Hilbert: Weiterführung der Methoden der Variationsrechnung. Akad. Wiss. Göttingen 1900, 291-296. ps, pdf. English Translation

Hilbert's Problems, English. Hilberts Probleme, deutsch.