1. USDA APHIS Veterinary Services Centers for Epidemiology and Animal Health Bull management practices on U.S. beef cow-calf operations http://www.aphis.usda.gov/animal_health/nahms/beefcowcalf/downloads/beef0708/Beef0708_is_BullMgmt.pdf
2. USDA APHIS 2011 National Animal Health Reporting System reportable disease list http://www.aphis.usda.gov/animal_health/nahrs/downloads/2011_nahrs_dz_list.pdf
3. Immunization and diagnosis in bovine reproductive tract infections;Corbeil;Adv Vet Med,1999
4. Experimental infection of bulls with Tritrichomonas foetus;Clark;Aust Vet J,1974
5. Letter: Infection of bulls with Tritrichomonas foetus through mating with infected heifers;Clark;Aust Vet J,1974