@book{94157,
	author = {López Vázquez, Gustavo.},
	title = {Variabilidad espacial y temporal de la sequía en el Estado de Zacatecas},
	publisher = {El autor,},
	year = {2007},
	address = {Chapingo, Méx. :},
	url = {http://10.13.5.2/tesis/105736.pdf}
}