1. M. Abramowitz and I.A. Stegun (Eds.) Handbook of Mathematical Functions. National Bureau of Standards, Applied Mathematics Series 55, U.S. Government Printing Office, Washington DC.,1964. (Reprinted by Dover Publications, 1970).
2. T. Ando, Majorization, doubly stochastic matrices, and comparison of eigenvalues, Linear Algebra Appl. 118 (1989), 163–248.
3. E. Artin, Einführung in die Theorie der Gammafunktion. Hamburger Mathematische Einzelschriften, Heft II. (Transl. by M. Butler, The Gamma Function (1964)) Holt, Rinehart & Winston, New York, 1931.
4. C.P. Chen, Complete monotonicity properties for a ratio of gamma functions, Univ. Beograd. Publ. Elektrotehn. Fac. Ser. Mat. 16 (2005), 26–28.
5. P.J. Davis, Leonard Euler’s integral: A historical profile of the gamma function, Amer. Math. Monthly 66 (1959), 849–869.