APA (7th ed.) Citation

Westerman, G. v., Rosenthal, H., & Ross, A. (1968). Opera. Sphere Books Limited.

Chicago Style (17th ed.) Citation

Westerman, Gerhart von, Harold Rosenthal, and Anne Ross. Opera. London: Sphere Books Limited, 1968.

MLA (9th ed.) Citation

Westerman, Gerhart von, et al. Opera. Sphere Books Limited, 1968.