Cita APA (7a ed.)
Associated Collectors of El Salvador & Freer, B. P. El Salvador Postal Stationery Handbook: Section 1 - Postcards.
Cita Chicago Style (17a ed.)
Associated Collectors of El Salvador 与 B. Phillips Freer. El Salvador Postal Stationery Handbook: Section 1 - Postcards.
Cita MLA (9a ed.)
Associated Collectors of El Salvador 与 B. Phillips Freer. El Salvador Postal Stationery Handbook: Section 1 - Postcards.
警告：这些引文格式不一定是100％准确.