Grigoryan, A. B. (2006). ALGEBRAIC MULTIGRID PRECONDITIONER FOR ELLIPTIC PROBLEMS WITH MIXED TYPE BOUNDARY CONDITIONS II. MULTIGRID PRECONDITIONER. Proceedings of the YSU A: Physical and Mathematical Sciences, 40(2 (210), 41–48. https://doi.org/10.46991/PYSU:A/2006.40.2.041