Cita APA (7th ed.)
O'Keefe, D. Philatelic Gems 1.
Cita Chicago (17th ed.)
O'Keefe, Donna. Philatelic Gems 1.
Cita MLA (9th ed.)
O'Keefe, Donna. Philatelic Gems 1.
Atenció: Aquestes cites poden no estar 100% correctes.