00601naa#a2200169#i#450# EN\\bibl\2887 20250406203051.7 2308-8877 20140616b2014####ek#y0engy0150####ca RUS RU Spectrum of a non -self-adjoint differential operators with block-triangular matrix coefficients Journal article Voronezh FSBE Institution of Higher Education Voronezh State University of Forestry and Technologies named after G.F. Morozov 2014 4 с. Journal article local Kholkin A. anni.editorum.ru