1. D.J. Griffiths, D.F. Schroeter, Introduction to Quantum Mechanics (Cambridge University Press, Cambridge, 2018)
2. L. Landau, E. Lifshitz, Quantum Mechanics: Non-Relativistic Theory, vol. 3 (Elsevier, Amsterdam, 2013)
3. S. Flugge, Practical Quantum Mechanics (Springer, Berlin, 2012)
4. A. Migdal, V. Krainov, A. Leggett, Approximation Methods in Quantum Mechanics (W.A. Benjamin, 1969)
5. E. Artin, The Gamma Function (Courier Dover Publications, 2015)