Giaquinta, Mariano: On differentiability of the extremals of variational integrals.
(English).
In:
John, Oldřich
and Kufner, Alois (eds.): Nonlinear Analysis, Function Spaces and Applications, Proceedings of the Spring School held in Písek, 1982.
Vol. 2.
BSB B. G. Teubner Verlagsgesellschaft, Leipzig, 1982.
pp. 38-92
