M. C. Thomaz, A. C. Silveira, R. N. Kronka, L. S. O. Nakaghi, and F. E. L. Budiño, “Sources of protein and slaughtering ages on the structure and ultra structure of the small intestine of weaned piglets”, Braz. J. Vet. Res. Anim. Sci., vol. 48, no. 5, pp. 408-418, Oct. 2011.