1. Di Benedetto, E., Trudinger, N.S. Harnack inequalities for quasi-minima of variational integrals,Ann. Inst. Henri Poincaré,1(4), 295–308, (1984).
2. De Giorgi, E. Sulla differeziabilita e l’analiticita degli integrali multipli regolari,Mem. Accad. Sci. Torino. Cl. Sci. Fis. Mat. Natur.,3(3), 25–43, (1957).
3. Kikuchi, N. Hölder estimates of solutions to difference-differential equations of elliptic-parabolic type, KSTS/RR-92/002, Keio University, 1992.
4. Ladyzhenskaya, O.A. and N.N. Ural’tseva.Linear and Quasilinear Elliptic Equation, Academic Press, New York, 1968.
5. Ladyzhenskaya, O.A., Solonnikov, V.A., and Ural’tseva, N.N.Linear and Quasilinear Equations of Parabolic Type, American Mathematical Society, Providence RI, 1968.