(1)
Tepoyan, L.; Grigoryan, H. ON DEGENERATE NONSELF-ADJOINT DIFFERENTIAL EQUATIONS OF FOURTH ORDER. Proc. YSU A: Phys. Math. Sci. 2012, 46 (3 (229), 29-33. https://doi.org/10.46991/PYSUA.2012.46.3.029.