T. P. Dias e Silva, S. C. Sousa Júnior, R. G. de Oliveira, and K. R. dos Santos, “Effect of exposure to solar radiation on physiological parameters and decline estimation of milk production by crossbred cows (Holstein x Gir) in the southern Piauí State, Brazil”, Com. Sci., vol. 3, no. 4, pp. 299–305, Dec. 2012.