2MAGASH A.The use of biotechniquesin yak reproduction[C]//Proceedings of the Second international congress on yak.Xining,China:Qinghai People' s Publish House,1997:175-178.
3YUN Z.Experiment on estrus synchronization for artificial insemination with frozen semen in yak[C]//Proceedings of the third international congress on yak.Addis Ababa,Ethiopia:International Livestock Research Institute,2000:349-352.