Duangjai Boonkusol, Kulnasan Saikhun, and Poonsuk Ratanaphumma, “Effects of Extender and Storage Time on Motility and Ultrastructure of Cooled-Preserved Boar Spermatozoa”, Agr. Nat. Resour., vol. 44, no. 4, pp. 582–589, Aug. 2010.