LutsenkoIe., and ProtasovI. V. “Relatively Thin and Sparse Subsets of Groups”. Ukrains’kyi Matematychnyi Zhurnal 63, no. 2 (February 25, 2011): 216-225. Accessed July 27, 2024. https://umj.imath.kiev.ua/index.php/umj/article/view/2712.