Haghighat-Jahromi, M., et al. “Role of Infectious Bronchitis Live Vaccine on Pathogenicity of H9N2 Avian Influenza Virus”. International Journal of Poultry Science, vol. 6, no. 11, Oct. 2007, pp. 838–841, https://doi.org/10.3923/ijps.2007.838.841.