1. Allen, W. R. Personal communication.
2. Transfer of Ova Between Horses and Donkeys;Allen,1972
3. Transfer of Mammalian Ova Between Species;Averill;Nature (London),1955
4. Genetic Control of the Duration of Gestation in Sheep;Bradford;J. Reprod. Fert.,1972
5. Fécondation Entre les Espèces Brebis et Chèvres et Obtention d'Hybrides Inter-espèces;Bratanov,1962