R. J. Raleigh and Turner, H. A.,
“Fall calving yields a bumper crop of benefits”,
Oregon's Agricultural Progress, no. 16. Oregon Agricultural Experiment Station, 1970.
H. A. Turner, Mc Innis, M., Angell, R. F., and Weber, D. W.,
“Factors Associated with Dystocia in Beef Heifers”,
The Professional Animal Scientist, vol. 8, no. 3, pp. 43 - 47, 1992.