Fahad M. Abdulkarim, Hasan Hussein Ali, Mohammed H. Mohammed, A. H. A.-Z. A. H. A. A.-A. “Effect of Vertical Irregularity in Multi-Storied Building Under Seismic Loading”. Design Engineering, Vol. 2021, no. 3, Apr. 2021, pp. 47 -59, http://www.thedesignengineering.com/index.php/DE/article/view/1206.