J. Papez, J. Liesen, and Z. Strakos, On distribution of the discretization and algebraic error in 1D Poisson model problem , submitted to Numerical Linear Algebra with Applications , in November 2012 . M. Rozloznik, A. Smoktunowicz, and J. Kopal, A Note on Iterative Refinement for Seminormal Equations, submitted to Applied Numerical Mathematics, in December 2011. I. Hnetynkova, M. Plesinger, and Z. Strakos, Core Problem within Linear Approximation Problem $AX \approx B$ with MultipleRight-Hand Sides, submitted to SIAM J. on Matrix Analysis and Applications, in July 2012.