1. Uğurlu, E.: Regular third-order boundary value problems. Appl. Math. Comput 343, 247–257 (2019)
2. Coddington, E.A., Levinson, N.: Theory of Ordinary Differential Equations. McGrow-Hill Book Company, New York (1955)
3. Dunford, N., Schwartz, J.T.: Linear Operators Part II: Spectral Theory. Interscience Publishers, New York (1963)
4. Naimark, M.A.: Linear Differential Operators Part I: Elementary Theory of Linear Differential Operators. George G. Harrap and Company, London (1966)
5. Everitt, W.N.: Self-adjoint boundary value problems on finite intervals. J. Lond. Math. Soc 37, 372–384 (1962)