1. Walter, J., Regular eigenvalue problems with eigenvalue parameter in the boundary condition, Math. Z., 1973, vol. 133, no. 44, pp. 301–302.
2. Fulton, C.T., Two-point boundary value problems with eigenvalue parameter contained in the boundary conditions, Proc. Roy. Soc. Edinburg Sect. A, 1977, vol. 77, no. 3–4, pp. 293–308.
3. Russakovskii, E.M., Operator treatment of boundary problems with spectral parameters entering via polynomials in the boundary conditions, Funct. Anal. Appl., 1975, vol. 9, no. 4, pp. 358–359.
4. Kerimov, N.B. and Allakhverdiev, T.I., On a boundary value problem. I, Differ. Equations, 1993, vol. 29, no. 1, pp. 45–50.
5. Kerimov, N.B. and Allakhverdiev, T.I., On a boundary value problem. II, Differ. Equations, 1993, vol. 29, no. 6, pp. 814–821.