Bondarenko, L. N., & Zhuk, P. F. (1997). Exact estima tes for the rate of convergence of the s-step method of steepest descent in eigenvalue problems. Ukrains’kyi Matematychnyi Zhurnal, 49(12), 1694–1699. https://umj.imath.kiev.ua/index.php/umj/article/view/5175