1. CAFFARELLI, L., FABES, E., KENIG, C.: Completely singular elliptic-harmonic measures. To appear on Indiana University Mathematics Journal
2. CAFFARELLI, L., FABES, E., MORTOLA, S., SALSA, S.: Boundary behavior of nonnegative solutions of elliptic operators in divergence form. To appear on Indiana University Mathematics Journal
3. DAHLBERG, B.E.J.: Estimates of harmonic measures. Arch. Rat. Mech. Analysis65, 275?288 (1977)
4. LITTMAN, W., STAMPACCHIA, G., WEINBERGER, H.F.: Regular points for elliptic equations with discontinuous coefficients. Ann. Sc. Norm. Sup. Pisa, Cl. Sci., Ser. III,XVII, 45?79 (1963)
5. MEYERS, N.G.: An LP-estimate for the gradient of solutions of second order elliptic divergence equations. Ann. Sc. Norm. Sup. Pisa, Cl. Sci., Ser. III,XVII, 189?206 (1963)