Merino, Ruben, Hilda Villegas, Jose A. Quintana, and Norma Calderon. 2011. “Comparison of the Virulence of Pathogenic Newcastle Disease Viruses Belonging to the Same or Different Genotypes”. International Journal of Poultry Science 10 (9): 713–720. https://doi.org/10.3923/ijps.2011.713.720.