A. Brenes, A. Viveros, I. Goñi, C. Centeno, F. Saura-Calixto, and I. Arija, “Effect of grape seed extract on growth performance, protein and polyphenol digestibilities, and antioxidant activity in chickens”, Span. j. agric. res., vol. 8, no. 2, pp. 326-335, Jul. 2010.