UdarD., Sharma R. K., and Srivastava J. B. “Strongly $P$ -Clean and Semi-Boolean Group Rings”. Ukrains’kyi Matematychnyi Zhurnal, Vol. 71, no. 12, Jan. 2020, pp. 1717-22, http://umj.imath.kiev.ua/index.php/umj/article/view/2289.