Hussain, Mujeeb, Qamruz Zaman, Lakhkar Khan, and Abdurrahman Sabir. “Improved Mean Estimators for Population Utilizing Dual Supplementary Characteristics under Simple Random Sampling : Mean Estimators Using Auxiliary Characteristics”. VFAST Transactions on Mathematics 12, no. 1 (May 7, 2024): 202–219. Accessed May 14, 2026. https://www.vfast.org/journals/index.php/VTM/article/view/1774.