1. R. Bank and J. Xu, A hierarchical basis multigrid method for unstructured meshes, in:10th GAMM-Seminar Kiel on Fast Solvers for Flow Problems, eds. W. Hackbusch and G. Wittum (Vieweg, Braunschweig, 1995).
2. R. Bank and J. Xu, An algorithm for coarsening unstructured meshes, Technical Report, Department of Mathematics, University of California, San Diego (1994).
3. T. Barth, Aspects of unstructured grids and finite-volume solvers for the Euler and Navier-Stokes equations, in:Special Course on Unstructured Grid Methods for Advection Dominated Flows (VKI, Belgium, 1992).
4. J. Bramble,Multigrid Methods, Notes on Mathematics (Pitman, 1994).
5. J. Bramble, J. Pasciak, J. Wang and J. Xu, Convergence estimates for product iterative methods with applications to domain decomposition, Math. Comp. 57 (1991) 1–21.