Oba, Eunice, et al. “Evaluation of Citric Acid and Fructose in the Semen of Nelore Sires of Various Age Groups”. Pesquisa Agropecuaria Brasileira, vol. 24, no. 1, Apr. 2014, pp. 37-41, doi:10.1590/S1678-3921.pab1989.v24.13746.