Dr. Sanjib Choudhury, and Bhupendra Kumar Singh. “An Efficient Class of Ratio-Cum-Dual to Product Estimator of Finite Population Mean in Sample Surveys”. Global Journal of Science Frontier Research, vol. 12, no. F12, Oct. 2012, pp. 1-11, https://journalofscience.org/index.php/GJSFR/article/view/669.