1. Grisvard, P. (1985) Elliptic Problems in Nonsmooth Domains. In: Monographs and Studies in Mathematics, Vol. 24, Pitman Advanced Publishing Program, Pitman Publishing Inc., Boston, MA, xiv 410p.
2. The Perron process applied to oblique derivative problems
3. Intermediate Schauder estimates for oblique derivative problems
4. Mixed boundary value problems for elliptic and parabolic differential equations of second order
5. Lieberman, G.M. (1987) Oblique Derivative Problems in Lipschitz Domains. I. Continuous Boundary Data. Bollettino dell’Unione Matematica Italiana B, 1, 1185-1210.