أحمد مهدي صالح. 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, v. 13, n. 52, p. 227–245, 2024. Disponível em: https://mail.journals.uokerbala.edu.iq/index.php/ijas/article/view/2653. Acesso em: 18 jan. 2025.