Grosser Ganzachen Katalog, Dr. S. Ascher, Vol. 2, Part 7, 1928, 1006-1019.
El Salvador - A study of the 1889 Overprints, Bruce Ball, The Oxcart, 1971, 24-28.
The September 15, 1909 San Salvador Issue, C. B. Bostwick, Philatelic Gazette, 1912, 155.
More About the 1903-04 Postal Cards, Pierre Cahen, El Faro, 1997, 7-11.
Salvador Airmails, Alex A. Cohen, 1930, 1-12.
Originals & Reprints of Seebeck Issues: A Scientific Method of Classification, Joseph D. Hahn, The Seebecker, 1992, 1-5.
The Seebeck Stamps Part I: 1890 – 1895, Joseph D. Hahn and Joseph M. Sousa, American Philatelic Congress Book, 1977, 11-37.
The Seebeck Stamps Part II: 1896 – 1899, Joseph D. Hahn and Joseph M. Sousa, American Philatelic Congress Book, 1978, 7-33.
Auction Catalog, Christies-Robson Lowe, Geneva III, The Unique Collection of Postage Stamps of El Salvador, formed by Joseph Hahn, 1979.
Stamps of Salvador, Parts 1 to 8, Joseph Leavy, Stanley Gibbons Monthly Journal, 1907-1908, 62-66, 93-97, 116-
119, 140-142, 187-191, 209-211, 226-230, 271-275.
The 1905-1906 Provisionals of Salvador, John Luff, Stanley Gibbons Monthly Journal, 1906, 269-271.
Salvador: The 1879 Issue : A New Look - Part 1, 2, 3, 4, J. R. W. Purves, The Mainsheet, 1979-1980, 3-12,
49-59, 80-87, 90-94.
El Salvador Postal Stationery, Finn Stjernholck, El Faro, 1991, 25-27.
El Salvador Postal Stationery: The Printed Private to Order Envelopes, Finn Stjernholck, El Faro, 1997, 17-20.
The world postal stationery catalogue, “Section 16: 1st ed. 1971 - Saar to Syria” edited by Edward G. Fladung, Higgins & Gage, Inc; Huntington Beach, Calif. 1971, 1-15.
English