1. Ashby, S.F., Holst, M.J., Manteuffel, T.A., Saylor, P.E.: The role of the inner product in stopping criteria for Conjugate Gradient iterations, BIT, 41, 26–52 (2001)
2. Ashby, S.F., Manteuffel, T.A., Saylor, P.E.: A taxonomy for Conjugate Gradient methods. SIAM J. Numer. Anal., 27, 1542–1568 (1990)
3. Axelsson, O.: Iterative Solution Methods. Cambridge University Press, Cambridge, 1994
4. Bai, Z.-Z., Golub, G.H., Ng, M.K.: Hermitian and skew-Hermitian splitting methods for non-Hermitian positive definite linear systems. SIAM J. Matrix Anal. Appl., 24, 603–626 (2003)
5. Benzi, M., Gander, M.J., Golub, G.H.: Optimization of the Hermitian and skew-Hermitian splitting iteration for saddle-point problems. BIT 43, 881–900 (2003)