Calculus of variations and nonlinear partial differential equations : lectures given at the C.I.M.E. Summer School held in Cetraro, Italy, June 27-July 2, 2005 - Ambrosio, Luigi; Dacorogna, Bernard; Marcellini, Paolo; Mascolo, Elvira; C.I.M.E. Summer School (Lecture notes in mathematics, 2008)