1. Brandt, G. W. 1958. Heterosis in dairy cattle as measured by birth weights, gestation lengths, certain body weights, and measurements, and mammary gland grades. Ph.D. Thesis. Ohio State University, Columbus.
2. Some genetic implications of maternal effects – An hypothesis of mammalian growth;Dickinson;J. Agr. Sci.,1960
3. Gregory, P. W., S. W. Mean, and W. M. Regan. 1951. A genetic analysis of prolonged gestation in cattle. Portugaliae Acta. Biol. Ser. A, Vol. R. B. Goldschmidt: 861.
4. Growth of first generation crossbred dairy calves;Hilder;J. Agr. Res.,1949
5. Prolonged gestation in bovine;Jasper;Cornell Vet.,1950