Sangwan, Vandana, et al. “Varicosity and Pregnancy Induced Blood Flow Changes in the Cranial Tibial Vein in Buffaloes: B-Mode and Doppler Ultrasound Study”. Buffalo Bulletin, vol. 36, no. 1, Sept. 2017, pp. 239-50, http://kuojs.lib.ku.ac.th/index.php/BufBu/article/view/1239.