@book{51393, author = {Santillana S.A. (Ecuador).}, title = {Estudios Sociales :}, publisher = {Grupo Santillana Ecuador, }, year = {2004}, series = {Mundos Santillana}, address = {Quito, Ecuador :}, note = {Instituto Ecuatoriano de la Propiedad Intelectual 002328 (19-02-2003)} }