(1971). Long-Term planning. United Nations.
Dyfyniad Arddull ChicagoLong-Term Planning. New York: United Nations, 1971.
Dyfyniad MLALong-Term Planning. United Nations, 1971.
Rhybudd: Mae'n bosib nad yw'r dyfyniadau hyn bob amser yn 100% cywir.
(1971). Long-Term planning. United Nations.
Dyfyniad Arddull ChicagoLong-Term Planning. New York: United Nations, 1971.
Dyfyniad MLALong-Term Planning. United Nations, 1971.