T. Q. Vui, J. Lohr, M. Kyule, K.-H. Zessin, and M. Baumann, “Antibody Levels against Newcastle Disease Virus, Infectious Bursal Disease Virus and Avian Influenza Virus in Rural Chickens in Viet Nam”, Int. J. Poult. Sci., vol. 1, no. 5, pp. 127–132, Aug. 2002, doi: 10.3923/ijps.2002.127.132.