Links
Bund Deutscher Philatelisten e.V.
Forum des Bundes Deutscher Philatelisten
American Philatelic Society
The Royal Philatelic Society of Canada
Postal History Society Of Canada
The British North America Philatelic Society
Vereniging voor USA en Canada Filatelie
The Precancel Stamp Society
Philatelistische Bibliothek Hamburg
Philatelistische Bibliothek Heinrich Köhler
Linn's Stamp News und Scott Katalog
Identifier for US Washington-Franklin Stamps of 1908-1922
Philatelic Foundation - Archiv
Philatelic Foundation
The Canal Zone Study Group
The International Philippine Philatelic Society
US Postage Stamps Identifier
Consilium Philatelicum
TPO & Seapost Society