Graham, W. F. (1975). Angels: God's secret agents. Doubleday.
Cita Chicago Style (17a ed.)Graham, William Franklin. Angels: God's Secret Agents. Garden City, N.Y: Doubleday, 1975.
Cita MLA (9a ed.)Graham, William Franklin. Angels: God's Secret Agents. Doubleday, 1975.
Precaución: Estas citas no son 100% exactas.