Joseph, H., and . K. M. . Sumaya. “Role of Qualitative Research in Preventing Customer Churn: A Case Study of Mobile Network Operators in Kenya”. Operations Research Society of Eastern Africa, vol. 7, no. 2, Dec. 2017, pp. 13-27, https://orseajournal.udsm.ac.tz/index.php/orsea/article/view/63.