Loan, R. W., H.- tang Tung, and J. B. Payne. “Comparative Efficacy and Duration of Immunity of Commercial Pasteurella Haemolytica Vaccines”. The Bovine Practitioner, vol. 1998, no. 32.1, Jan. 1998, pp. 18-21, doi:10.21423/bovine-vol1998no32.1p18-21.