عبد العزيز احمد ريكان. “On Some Ratio and Regression Estimators for the Finite Population Variance in Two Phase Sampling”. IRAQI JOURNAL OF STATISTICAL SCIENCES 10, no. 2 (December 1, 2010): 117–132. Accessed September 18, 2025. https://ojs.uomosul.edu.iq/index.php/stats/article/view/29054.