Ding-ping, Bai, Yu Cheng-jiang, and Chen Yu-lin. 2012. “Association Between AA-NAT Gene Polymorphism and Reproductive Performance in Sheep”. Electronic Journal of Biotechnology 15 (2). Valparaíso, Chile. https://preprints.pucv.cl/index.php/ejbiotechnology/article/view/v15n2-6.