Wikse, S. E., Rogers, G. M., Ramachandran, S., Engelken, T. J., Epperson, W. B., Larson, R. L., Maas, J., Richey, E. and Bolin, C. (2007) “Herd prevalence and risk factors of Leptospira infection in beef cow/calf operations in the United States: Leptospira borgpetersenii Serovar Hardjo”, The Bovine Practitioner, 41(1), pp. 15–23. doi: 10.21423/bovine-vol41no1p15-23.