Cita APA (7th ed.)

Apel, W. (1958). Gregorian chant. Indiana University Press.

Cita Chicago (17th ed.)

Apel, Willi. Gregorian Chant. Bloomington: Indiana University Press, 1958.

Cita MLA (9th ed.)

Apel, Willi. Gregorian Chant. Indiana University Press, 1958.