APA (7th ed.) Citation

Voegelin, C. F., & Voegelin, F. M. (1978). Classification and index of the world's languages (2nd printing.). Elsevier.

Chicago Style (17th ed.) Citation

Voegelin, Charles F., and Florence M. Voegelin. Classification and Index of the World's Languages. 2nd printing. New York [etc.]: Elsevier, 1978.

MLA (9th ed.) Citation

Voegelin, Charles F., and Florence M. Voegelin. Classification and Index of the World's Languages. 2nd printing. Elsevier, 1978.