Piętka, Marek. “A Note on the Increase of the Operational Function Exp(λΣ_{k=1}^{n}A_{k}s^{p_k})”. Annales Mathematicae Silesianae 3 (January 30, 1990): 107-114. Accessed May 16, 2024. https://journals.us.edu.pl/index.php/AMSIL/article/view/14309.