Hadi, Inaam M. A., and Ghaleb A. Humod. “Strongly (Completely) Hollow Sub-Modules II”. Ibn AL-Haitham Journal For Pure and Applied Sciences, vol. 26, no. 1, May 2017, pp. 292-0, https://jih.uobaghdad.edu.iq/index.php/j/article/view/537.