Nacy, Dr. Somer M., Dr.Hikmat Al-Rawi, and Mohammed M. Hasan. 2017. “A Study Of Strengthening Circular Diaphragm By Ring-Shaped Concentric Ribs”. Al-Khwarizmi Engineering Journal 2 (1): 15-34. https://www.alkej.uobaghdad.edu.iq/index.php/alkej/article/view/2.