Downs, R. (1983). Books that changed the world. New American.
Dyfyniad Arddull ChicagoDowns, Robert. Books That Changed the World. New York: New American, 1983.
Dyfyniad MLADowns, Robert. Books That Changed the World. New American, 1983.
Rhybudd: Mae'n bosib nad yw'r dyfyniadau hyn bob amser yn 100% cywir.