Marcinkiewicz' interpolation theorem15 Method of rotations51 Nontangential cone12 Nontangential limit12 Nontangential maximal function12 Poisson kernel29 Principal value operator (PVO)18 Rellich identity55 Schwartz class S17 Singular integral operators (SIO)17 Solution to the Dirichlet Problem12 Special Lipschitz domain12 Subsolution60 Supersolution60