Ismail, Mahmud, and Mohsin Jweeg. “Natural Frequencies of Multi-Irregular Span Beams under Elastic Supports by Modal Analysis Method”. Al-Nahrain Journal for Engineering Sciences 18, no. 2 (June 1, 2017): 284 - 293. Accessed January 19, 2022. https://nahje.com/index.php/main/article/view/190.