1. M. Abramowitz, I.A. Stegun (Eds.), Handbook of Mathematical Functions with Formulas, Graphs, and Mathematical Tables, Dover, New York, 1965.
2. Some classes of completely monotonic functions;Alzer;Ann. Acad. Scient. Fennicae,2002
3. H. Alzer, C. Berg, Some classes of completely monotonic functions, II, The Ramanujan J., to appear.
4. Signs of derivatives and analytic behavior;Boas;Amer. Math. Monthly,1971
5. Inequalities involving gamma and psi functions;Clark;Anal. Appl.,2003