1. Photoperiod: main proximal and distal factor of the circannual cycle of reproduction in farm mammals;Ortavant;Oxf. Rev. of Reprod. Biol.,1985
2. The time of foaling of thoroughbred mares;Rossdale;J. Reprod. Fertil.,1967
3. Factors which influence parturition in the mare and development of the foal;Campitelli;Appl. Anim. Ethol.,1982
4. Untersuchungen über die Geburt der Saügetiere;Naaktgeboren;Th. Univ. Amsterdam,1963
5. Observaciones del parto de Alpaca;Bustinza,1970