In this note we present some new and structural inequalities for digamma, polygamma and inverse polygamma functions. We also extend, generalize and refine some known inequalities for these important functions. © 2006 Elsevier Inc. All rights reserved.
Batir, N. (2007). On some properties of digamma and polygamma functions. Journal of Mathematical Analysis and Applications, 328(1), 452–465. https://doi.org/10.1016/j.jmaa.2006.05.065