1. Lectures on Elliptic Boundary Value Problems;Agmon,1965
2. Projection methods for Dirichlet's problem in approximating polygonal domains with boundary value corrections;Bramble;Math. Comp.,1972
3. Lebesgue spaces of differentiable functions and distributions, Partial Differential Equations;Calderón;Proc. Symp. Pure Math.,1961
4. J. E. Dendy, Thesis, Rice University, 1971.
5. also to appear in SIAM Numer. Anal.