“A Study of Some Factors Affecting Reproductive Traits in a Small Producer Crossbred Dairy Cows in the Sudan”. The Sudan Journal Of Animal Production المجلة السودانية للانتاج الحيواني, vol. 17, no. 17, June 2004, p. 9, https://sud-jap.sd/Journal/index.php/sjap/article/view/148.