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 y B. Phillips Freer. El Salvador Postal Stationery Handbook: Section 1 - Postcards.
Cita MLA (9a ed.)
Associated Collectors of El Salvador y B. Phillips Freer. El Salvador Postal Stationery Handbook: Section 1 - Postcards.
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