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3. K. Stuben, A Review of Algebraic Multigrid (GMD Report 69, 1999).
4. K. Stuben, Algebraic Multigrid (AMG): an Introduction with Applications (GMD Report 70, 1999).
5. J. R. Wallis, Incomplete Gaussian Elimination as a Preconditioning for Generalized Conjugate Gradient Acceleration (SPE 12265, 1983).