Generalized Robin Boundary Conditions, Robin-to-Dirichlet Maps, and   Krein-Type Resolvent Formulas for Schr\"odinger Operators on Bounded   Lipschitz Domains
  We study generalized Robin boundary conditions, Robin-to-Dirichlet maps, and Krein-type resolvent formulas for Schr\"odinger operators on bounded Lipschitz domains in $\bbR^n$, $n\ge 2$. We also discuss the case of bounded $C^{1,r}$-domains, $(1/2)<r<1$. 
Fritz Gesztesy and Marius Mitrea