APA (7th ed.) Citation

Princeton Language Institute. (1993). 21st century spelling dictionary. Dell Pub.

Chicago Style (17th ed.) Citation

Princeton Language Institute. 21st Century Spelling Dictionary. New York: Dell Pub, 1993.

MLA (9th ed.) Citation

Princeton Language Institute. 21st Century Spelling Dictionary. Dell Pub, 1993.

Warning: These citations may not always be 100% accurate.