Mohammed Shafiqu, Qassun S., and Ahmed A. Yassen. “Time-Dependent Behavior of Excavation in Cohesive Soils Using the Bounding Surface Model”. Al-Nahrain Journal for Engineering Sciences, vol. 14, no. 1, Mar. 2011, pp. 1-12, https://nahje.com/index.php/main/article/view/596.