Shortest paths : variational problems / by L. A. Lyusternik ; translated and adapted from the Russian, by P. Collins and Robert B. Brown. Liusternik, L. A. (Lazar Aronovich), 1899- Curves on surfaces. Calculus of variations. QA316 L6813 517.383 MAS Oxford : Pergamon Press ; New York : Distributed in the Western Hemisphere by Macmillan, 1964. 1964. 1964 Text x, 102 p. : eng Popular lectures in mathematics (New York, N.Y.) ; v. 13 Survey of recent East European mathematical literature