Toader, Gheorghe. “Supermultiplicative Sequences in Semigroups”. Rev. Anal. Numér. Théor. Approx. 23, no. 2 (August 1, 1994): 227–230. Accessed May 19, 2024. https://ictp.acad.ro/jnaat/journal/article/view/1994-vol23-no2-art11.