1. W. Greiner, Relativistic Quantum Mechanics: Wave Equations (Springer, Berlin, 2000).
2. L.D. Landau, E.M. Lifshitz, Quantum Mechanics, Non- Relativistic Theory (Pergamon, New York, 1977).
3. L.I. Schiff, Quantum Mechanics (McGraw Hill, New York, 1995).
4. P.A. Dirac, The Principles of Quantum Mechanics (Clarendon Press, Oxford, 1958).
5. P.O. Okoi, C.O. Edet, T.O. Magu, Rev. Mex. Fis. 66, 1 (2020)