@Book{BDG20080011116, title = "Libros del saber de Astronom\'{\i}a del Rey Alfonso X de Castilla", author = "Alfonso X , Rei de Castela, 1221-1284", publisher = "Madrid : [s.n.]", editor = "[s.n.]", URL = "http://biblioteca.galiciana.gal/es/consulta/registro.do?id=4706", year = "1863", }