GUIMARÃES FILHO, C.; SOARES, J. G. G. A physical model evaluation of a caatinga/buffel grass/leucaena integrated system for cattle production in the semi-arid region. I. Cow-calf operation. Pesquisa Agropecuaria Brasileira, v. 34, n. 9, p. 1721–1727, 1 Sep.1999.