Ba'Its, Hamzah Abdul, et al. “Combination of Program Evaluation and Review Technique (PERT) and Critical Path Method (CPM) for Project Schedule Development”. International Journal of Integrated Engineering, vol. 12, no. 3, Feb. 2020, pp. 68-75, https://publisher.uthm.edu.my/ojs/index.php/ijie/article/view/4207.