I am seeking some references that deal with nonlinear elliptic PDEs with homogeneous Neumann boundary conditions in bounded domains with non-smooth boundaries (Lipschitz boundaries might be okay, though).
Specifically, any results on the regularity of weak solutions?
What I have in mind are results similar to those found in Evans's PDEs about interior and boundary $H^2$ regularity of weak solutions.
It does not have to be fully nonlinear! Semi-linear or quasi-linear would be good for a start.
I am aware of Grisvard's Elliptic Problems in Nonsmooth Domains but it only deals with linear equations (mainly Laplace equation).
