APA (7th ed.) Citation

Voegelin, C. F., & Voegelin, F. M. (1977). Classification and index of the world's languages. Elsevier.

Chicago Style (17th ed.) Citation

Voegelin, C. F., and F. M. Voegelin. Classification and Index of the World's Languages. New York: Elsevier, 1977.

MLA (9th ed.) Citation

Voegelin, C. F., and F. M. Voegelin. Classification and Index of the World's Languages. Elsevier, 1977.