Readers Digest Asso. (1980). Natural wonders of the world. RDA.
Chicago Style (17th ed.) CitationReaders Digest Asso. Natural Wonders of the World. New York: RDA, 1980.
MLA (9th ed.) CitationReaders Digest Asso. Natural Wonders of the World. RDA, 1980.
Warning: These citations may not always be 100% accurate.