Cita APA (7a ed.)

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

Cita Chicago Style (17a ed.)

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

Cita MLA (9a ed.)

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