1. Agricultural Research Service. 1976. State codes or prefix codes for dairy cattle records. DHI Letter, USDA, ARS-NE-60-4, p. 9.
2. Estimation of genetic trends in dairy cattle populations;Burnside;J. Dairy Sci.,1967
3. Dickinson, F. N., R. L. Powell, and H. D. Norman. 1976. An introduction to the USDA-DHIA Modified Contemporary Comparison. USDA Prod. Res. Rpt. No. 165, p. 1.
4. Production and stability trends in dairy cattle;Everett;J. Dairy Sci.,1976
5. Biases in dairy sire evaluation attributable to genetic trend and female selection;Hargrove;J. Dairy Sci.,1971