1. Atkinson, F.V., Discrete and Continuous Boundary Problems, New York-London: Academic Press, 1964. Translated under the title: Diskretnye i nepreryvnye granichnye zadachi, Moscow: Mir, 1968.
2. Collatz, L., Eigenwertaufgaben mit Technischen Anwendungen, Leipzig: Akademische Verlagsgesellschaft Geest & Portig K.-G., 1963. Translated under the title: Zadachi na sobstvennye znacheniya, Moscow: Nauka, 1968.
3. Gasymov, T.B. and Mammadova, Sh.J., On convergence of spectral expansions for one discontinuous problem with spectral parameter in the boundary condition, Trans. Natl. Acad. Sci. Azerb., 2006, vol. 26, no. 4, pp. 103–116.
4. Gasymov, T.B. and Huseynli, A.A., The basis properties of eigenfunctions of a discontinuous differential operator with a spectral parameter in boundary condition, Proc. Inst. Math. Mech. Natl. Acad. Sci. Azerb., 2011, vol. 35, no. 43, pp. 21–32.
5. Gasymov, T.B. and Huseynli, A.A., On the completeness of eigenfunctions and associated functions of one discontinuous second-order differential operator, Dokl. Nats. Akad. Nauk. Azerb., 2012, vol. 63, no. 1, pp. 3–7.