Singh, R. ., S. . Malik, M. K. . Chaudhary, H. K. . Verma, and A. . Adewara. “A GENERAL FAMILY OF RATIO-TYPE ESTIMATORS IN SYSTEMATIC SAMPLING”. Journal of Reliability and Statistical Studies, vol. 5, no. 01, June 2012, pp. 73-82, https://journals.riverpublishers.com/index.php/JRSS/article/view/21941.