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Dyfyniad Arddull ChicagoCunningham, William P., và Mary Ann Cunningham. Environmental Science: A Global Concern. Twelfth ed. New York: McGraw-Hill Companies, Inc., 2012.
Dyfyniad MLACunningham, William P., và Mary Ann Cunningham. Environmental Science: A Global Concern. Twelfth ed. New York: McGraw-Hill Companies, Inc., 2012.
Rhybudd: Mae'n bosib nad yw'r dyfyniadau hyn bob amser yn 100% cywir.