1. Abeygunawardena, H. and Dematawewa, C. M. B., 2004. Pre-pubertal and postpartun anestrus in tropical Zebu Cattle. Animal Reproduction Science, 83, 373 –387. doi: 10.1016/j.anireprosci.2004.05.006
2. Ahmed, M. A., Ahmed, B. T., Lutfi, M. A. M. and Peters, K. J., 2007. Milk production and reproduction traits of different grades of zebu X Friesian crossbreds under semi-arid conditions. Arch. Tierz. Dummerstorf, 50, 240–249.
3. Asimwe, L. and Kifaro, G. C., 2007. Effect of breed, season, year and parity on reproductive performance of dairy cattle under smallholder production system in Bukoba district, Tanazania. Livestock Research for Rural Development, 19, http://www.cipav.org.co/lrrd/lrrd19/10/asim1952.htm
4. Azage, T., Geleto, A., Osuji, P., Kassa, T. and Franceschinin, R., 1994. Influence of dietary supplementation and partial suckling on body weight and on lactation and reproductive performance of primiparous Boran (Bos indicus) cows. Ethiopian Journal of Agricultural Sciences, 123, 267–273.
5. Butler, W.R., 2000. Nutritional interactions with reproductive performance in dairy cattle. Animal Reproduction Science, 60, 449–457. doi: 10.1016/S0378-4320(00)00076-2