Vaz, A. C. N., R. de Albuquerque, M. L. Brisola, D. C. Z. Donato, and P. D. S. R. Garcia. “Effect of Phytase Supplementation With Different Levels of Crude Protein and Available Phosphorum on Performance and Crude Protein Excretion of Broiler Chickens”. Brazilian Journal of Veterinary Research and Animal Science, vol. 46, no. 2, Apr. 2009, pp. 107-11, doi:10.11606/issn.1678-4456.bjvras.2009.26756.