1. American Hereford Association
2005. North American Hereford National Cattle Evaluation: Genetic Trend. Available: http://www.hereford.org/Acrobat/Perf/S05_Trend.pdf Accessed June 12, 2005.
2. Factors affecting breeding soundness classification of beef bulls examined at the Western College of Veterinary Medicine;Barth;Can. Vet. J.,2002
3. A manual for use of MTDFREML;Boldman,1995