Yuanzhe Xi Ruipeng Li Yousef Saad An Algebraic Multilevel Preconditioner with Low-Rank Corrections for Sparse Symmetric Matrices. 235-259 2016 37 SIAM J. Matrix Anal. Appl. 1 https://doi.org/10.1137/15M1021830 db/journals/siammax/siammax37.html#XiLS16