Piętka, M. (1990) “A note on the increase of the operational function exp(λΣ_{k=1}^{n}A_{k}s^{p_k})”, Annales Mathematicae Silesianae, 3, pp. 107–114. Available at: https://trrest.vot.pl/ojsus/index.php/AMSIL/article/view/14309 (Accessed: 7 May 2025).