Neto, José de Souza, et al. “Socioeconomical Analysis of Goats and Sheep Exploitation in Piauí State, Brazil”. Pesquisa Agropecuaria Brasileira, vol. 30, no. 8, Aug. 1995, pp. 1017-30, doi:10.1590/S1678-3921.pab1995.v30.4392.