Cita APA (7th ed.)
Graham, B. (1975). Angels: God's secret agents. Doubleday.
Cita Chicago (17th ed.)
Graham, Billy. Angels: God's Secret Agents. Garden City, N.Y.: Doubleday, 1975.
Cita MLA (9th ed.)
Graham, Billy. Angels: God's Secret Agents. Doubleday, 1975.
Atenció: Aquestes cites poden no estar 100% correctes.