Elsgolts, L. Y. (1970). Differential equations and the calculus of variations.
Chicago Edition CitationElsgolts, L; Yankovsky. Differential Equations and the Calculus of Variations. Mir Publishers, Moscow, 1970.
MLA Edition CitationElsgolts, L; Yankovsky. Differential Equations and the Calculus of Variations. 1970.
Warning: These citations may not always be 100% accurate.