From the reviews: "...the book contains a wealth of material essential
to the researcher concerned with multiple integral variational problems
and with elliptic partial differential equations. The book not only
reports the researches of the author but also the contributions of his
contemporaries in the same and related fields. The book undoubtedly will
become a standard reference for researchers in these areas. ...The book
is addressed mainly to mature mathematical analysts. However, any
student of analysis will be greatly rewarded by a careful study of this
book."
M. R. Hestenes in Journal of Optimization Theory and Applications
"The work intertwines in masterly fashion results of classical analysis,
topology, and the theory of manifolds and thus presents a comprehensive
treatise of the theory of multiple integral variational problems."
L. Schmetterer in Monatshefte für Mathematik
"The book is very clearly exposed and contains the last modern theory in
this domain. A comprehensive bibliography ends the book."
M. Coroi-Nedeleu in Revue Roumaine de Mathématiques Pures et
Appliquées