1. A generalized SSOR;Axelsson;BIT,1972
2. PLTMG User's Guide;Bank,1981
3. A multigrid optimal order solver for elliptic boundary value problems: the finite difference case;Douglas,1984
4. An approximate factorization procedure for solving self-adjoint elliptic difference equations;Dupont;SIAM J. Numer. Anal.,1968
5. Efficient implementation of a class of conjugate gradient methods;Eisenstat;SIAM J. Sci. Stat. Comp.,1981