@book{6019,
	author = {Schopenhauer, Arthur  and Unamuno, Miguel de},
	title = {Sobre la voluntad en la naturaleza},
	publisher = {Alianza},
	year = {2009},
	series = {Humanidades},
	address = {Madrid},
	edition = {1a. edición },
	note = {Incluye notas y cuadro cronológico}
}