Nečas J.: Direct Methods in the Theory of Elliptical Equations. (in French), Academia, Prague 1967.
 Poracká Z.: An application of the variational calculus to non-linear partial differential equations of elliptic type. (in Slovak), Thesis, Prague 1965.
 Hlaváček I., Nečas J.: On inequalities of Korn's type
. (in print). Zbl 0193.39002
 Vainberg M. M.: Variational methods of study of nonlinear operators. (in Russian) Moscow 1956.