1. Hypersurfaces with bounded Levi form;Bedford;Indiana Univ. Math. J.,1978
2. Principe du maximum, inégalité de Harnack et unicitè du problème de Cauchy pour les opérateurs elliptic dégénérés;Bony;Ann. Inst. Fourier (Grenoble),1969
3. The Dirichlet problem for non-linear second order elliptic equations III;Caffarelli;Acta Math.,1985
4. A comparison theorem for the Levi equation;Citti;Rend. Mat. Acc. Lincei (s.9),1993
5. J.P. D'Angelo, Several Complex Variables and the Geometry of Real Hypersurfaces, Studies in Advanced Mathematics, CRC Press, Boca Raton, FL, 1993.