2 citations to https://www.mathnet.ru/rus/znsl87

1. Aliyev Z.S., “Some Global Results for Nonlinear Fourth Order Eigenvalue Problems”, Cent. Eur. J. Math., 12:12 (2014), 1811–1828            
2. Aliyev Z.S., “Basis Properties of a Fourth Order Differential Operator with Spectral Parameter in the Boundary Condition”, Cent. Eur. J. Math., 8:2 (2010), 378–388