2 citations to https://www.mathnet.ru/eng/vmumm1793

1. E. A. Shiryaev, “Basis Property of Eigen- and Associated Functions of an Operator with Nondense Domain of Definition in the Example of the Orr–Sommerfeld problem”, Math. Notes, 102:6 (2017), 867–872          
2. J. Ben Amara, A. A. Vladimirov, A. A. Shkalikov, “Spectral and Oscillatory Properties of a Linear Pencil of Fourth-Order Differential Operators”, Math. Notes, 94:1 (2013), 49–59