Alsaqqar, A., B. Khudair, and R. Jbbar. “Condition Assessment and Rehabilitation for Trunk Sewer Deterioration Based on Semi-Markov Model”. Association of Arab Universities Journal of Engineering Sciences, Vol. 25, no. 5, Jan. 2019, pp. 14-27, https://jaaru.org/index.php/auisseng/article/view/215.