Topics in calculus of variations lectures given at the 2nd 1987 session of the Centro internazionale matematico estivo (C.I.M.E.) held at Montecatini Terme, Italy, July 20-28, 1987 / M. Giaquinta (ed.). - Giaquinta, Mariano, 1947- (Lecture notes in mathematics (Springer-Verlag) ;, 1989)