Cita APA (7th ed.)
United States Postal Service. History of the United States Postal Service: 1775-1993.
Cita Chicago (17th ed.)
United States Postal Service. History of the United States Postal Service: 1775-1993.
Cita MLA (9th ed.)
United States Postal Service. History of the United States Postal Service: 1775-1993.
Atenció: Aquestes cites poden no estar 100% correctes.