Cita APA (7th ed.)
Apel, W. (1958). Gregorian chant. Burns, Oates & Washbourne.
Cita Chicago (17th ed.)
Apel, Willi. Gregorian Chant. London: Burns, Oates & Washbourne, 1958.
Cita MLA (9th ed.)
Apel, Willi. Gregorian Chant. Burns, Oates & Washbourne, 1958.
Atenció: Aquestes cites poden no estar 100% correctes.