أحمد مهدي صالح (2024) “Development of a reduced estimator to estimate the variance and covariance matrix with large dimensions using hyperbolic trigonometric functions - (Chemical properties of the soil of the Tigris Basin in Wasit Governorate)”, Iraqi Journal for Administrative Sciences. كربلاء، جمهورية العراق, 13(52), pp. 227–245. Available at: https://mail.journals.uokerbala.edu.iq/index.php/ijas/article/view/2653 (Accessed: 18 January 2025).