Ruiz, Teodoro M., and Efraín Cancel-Medina. “Performance of Holstein Cows Fed Two Levels of Concentrate Supplementation and Ruminally Undegraded Protein”. The Journal of Agriculture of the University of Puerto Rico, vol. 90, no. 1-2, Apr. 2006, pp. 9-26, doi:10.46429/jaupr.v90i1-2.2958.