Conservation Criteria, Canonical Transformations, and Integral Invariants in the Field Theory of Carathéodory for Multiple Integral Variational Problems. (Short Communication). Hanno Rund (1975) Aequationes mathematicae
Conservation criteria, canonical transformations, and integral invariants in the field theory of Carathéodory for multiple integral variational problems. Hanno Rund (1975) Aequationes mathematicae
Critical Point Theorems for Indefinite Functionals. Vieri Benci, Paul H. Rabinowitz (1979) Inventiones mathematicae