V. P. Shchedrik, “On the Interdependence between Invariant Multipliers of a Block-Triangular Matrix and Its Diagonal Blocks”, Mat. Zametki, 90:4 (2011), 599–612; Math. Notes, 90:4 (2011), 584–596
P. S. Kazimirskii, V. P. Shchedrik, “Solutions of matrix polynomials of one-sided equations”, Dokl. Akad. Nauk SSSR, 304:2 (1989), 271–274; Dokl. Math., 39:1 (1989), 45–47