Grigoryan, A. B. “ALGEBRAIC MULTIGRID PRECONDITIONER FOR ELLIPTIC PROBLEMS WITH MIXED TYPE BOUNDARY CONDITIONS I. TWO-GRID PRECONDITIONERS”. Proceedings of the YSU A: Physical and Mathematical Sciences 40, no. 1 (209) (March 7, 2006): 37–48. Accessed November 23, 2024. https://journals.ysu.am/index.php/proceedings-phys-math/article/view/vol40_no1_2006_pp037-048.