Indlekofer, K.-H., and E. Kaya. “Remarks on Number Theory over Additive Arithmetical Semigroups”. Ukrains’kyi Matematychnyi Zhurnal 72, no. 3 (March 28, 2020): 371-390. Accessed April 19, 2024. https://umj.imath.kiev.ua/index.php/umj/article/view/6042.