Bernard Dacorogna 
Direct Methods in the Calculus of Variations [PDF ebook] 

Convex analysis and the scalar case.- Convex sets and convex functions.- Lower semicontinuity and existence theorems.- The one dimensional case.- Quasiconvex analysis and the vectorial case.- Polyconvex, quasiconvex and rank one convex functions.- Polyconvex, quasiconvex and rank one convex envelopes.- Polyconvex, quasiconvex and rank one convex sets.- Lower semi continuity and existence theorems in the vectorial case.- Relaxation and non-convex problems.- Relaxation theorems.- Implicit partial differential equations.- Existence of minima for non-quasiconvex integrands.- Miscellaneous.- Function spaces.- Singular values.- Some underdetermined partial differential equations.- Extension of Lipschitz functions on Banach spaces.