Mm. Dougherty, HIGHER GRADIENT INTEGRABILITY OF MINIMIZERS FOR A POLYCONVEX CASE IN 2-DIMENSIONS, SIAM journal on mathematical analysis, 28(3), 1997, pp. 530-538
Local LP-estimates, 1 < p < infinity, of the gradient are proved for m
inimizers of certain functionals whose integrands have quadratic growt
h in the gradient and are polyconvex ''at infinity.'' Both variations
of dependent and independent variables of the minimizers are used to d
erive equations from which Calderon-Zygmund theory gives the result. H
older continuity of the minimizers will follow as a corollary.