HuangT.-Z., and WuC.-Y. “Perturbation and Error Analyses of Partitioned LU factorization for Block Tridiagonal Linear Systems”. Ukrains’kyi Matematychnyi Zhurnal, Vol. 68, no. 12, Dec. 2016, pp. 1683-95, https://umj.imath.kiev.ua/index.php/umj/article/view/1953.