Ungerfeld, R., and F. Sanchez-Davila. “Oestrus Synchronization in Postpartum Autumn-Lambing Ewes: Effect of Postpartum Time, Parity, and Early Weaning”. Spanish Journal of Agricultural Research, Vol. 10, no. 1, Jan. 2012, pp. 62-68, doi:10.5424/sjar/2012101-233-11.