Barker, J. A. (1992). Future edge. New York: William Morrow and Company.
Dyfyniad Arddull ChicagoBarker, Joel Arthur. Future Edge. New York: William Morrow and Company, 1992.
Dyfyniad MLABarker, Joel Arthur. Future Edge. New York: William Morrow and Company, 1992.
Rhybudd: Mae'n bosib nad yw'r dyfyniadau hyn bob amser yn 100% cywir.