J. Martin Polo, C. Valle Gutierrez, A. Blanco de Pablos, and M. Sánchez Rodríguez, “Forages resources in "dehesa" system: fertilization, tillage and forage sowing. I. Influence to the environment (soil and vegetation)”, Span. j. agric. res., vol. 1, no. 1, pp. 23-33, Mar. 2003.