books.google.com - Suitable for those concerned with multiple integral variational problems and with elliptic partial differential equations, this book presents a comprehensive treatise of the theory of multiple integral variational problems....http://books.google.com/books/about/Multiple_Integrals_in_the_Calculus_of_Va.html?id=-QNKm1PBohsC&utm_source=gb-gplus-shareMultiple Integrals in the Calculus of Variations
Suitable for those concerned with multiple integral variational problems and with elliptic partial differential equations, this book presents a comprehensive treatise of the theory of multiple integral variational problems.