Tangential limits of monotone Sobolev functions.
Teoremi di confronto di tipo Harnack per funzioni armoniche in domini con frontiera hölderiana
The Absolute Continuity of Elliptic Measure Revisited.
The boundary Harnack principle for the fractional Laplacian
We study nonnegative functions which are harmonic on a Lipschitz domain with respect to symmetric stable processes. We prove that if two such functions vanish continuously outside the domain near a part of its boundary, then their ratio is bounded near this part of the boundary.