R. Merino, H. Villegas, J. A. Quintana, and N. Calderon, “Comparison of the Virulence of Pathogenic Newcastle Disease Viruses Belonging to the Same or Different Genotypes”, Int. J. Poult. Sci., vol. 10, no. 9, pp. 713–720, Aug. 2011, doi: 10.3923/ijps.2011.713.720.