Cita APA (7th ed.)
Billings, R. R., Laurence, M., & Shelton, W. ". México: Postal issue of 1874-1883 (Hidalgo Heads).
Cita Chicago (17th ed.)
Billings, R. R., Michael Laurence, i W.E. "Bill" Shelton. México: Postal Issue of 1874-1883 (Hidalgo Heads).
Cita MLA (9th ed.)
Billings, R. R., et al. México: Postal Issue of 1874-1883 (Hidalgo Heads).
Atenció: Aquestes cites poden no estar 100% correctes.