1Alibert, J. J. and Dacorogna, B.. An example of a quasiconvex function that is not polyconvex in two dimension. Arch. Rational Mech. Anal. 117 (1992) 155–166.
2Ball, J. M.. Convexity conditions and existence theorems in nonlinear elasticity. Arch. Rational Mech. Anal. 64 (1977), 337–403.
3Brezis, H.. Analyse Fonctionnelle (Paris: Masson, 1983).
4Dacorogna, B.. Direct Methods in the Calculus of Variations (Berlin: 1989).
5Ekeland, I.. Non convex minimization problem. Bull. Amer. Math. Soc. 1 (3) (1979) 443–474.
6Gehring, F.. The Lp integrability of the partial derivatives of quasiconformal mapping. Ada Math. 130 (1973), 265–277.
7Giaquinta, M. and Modica, G.. Regularity results for some classes of higher order non linear elliptic systems. J. Reine Angew. Math. 311/312 (1979), 145–169.
8Kohn, R. V.. The relaxation of a double-well energy (to appear).
9Kohn, R. V. and Strang, G.. Optimal design and relaxation of variational problems I, II and III. Comm. Pure Appl. Math. 39 (1986), 113–137; 139–182; 353–377.
10Marcellini, P. and Sbordone, C.. On the existence of minima of multiple integrals. J. Math. Pures Appl. 62 (1983), 1–9.
11Morrey, C. B.. Quasiconvexity and semicontinuity of multiple integrales. Pacific J. Math. 2 (1952), 25–53.
12Morrey, C. B.. Multiple Integrals in the Calculus of Variations (Berlin: Springer, 1966).
13Simader, C. G.. On Dirichlet's Boundary Value Problem, Lecture Notes in Math. 268 (Berlin: Springer, 1972).
14Sverak, V.. Quasiconvex functions with subquadratic growth (to appear).