Bibliography

I have found information in the following books:

• "Die Welt des Ansichtskartensammeins" - Thomas Furst, Gunter Formery
• "A Guide Book of Collectible Postcards" - Q. David Bowers, Mary L. Martin
• https://undividedbackpostcard.com
• "HATEMAIL – Anti-semitism On Picture Postcards" by Salo Aizenberg. Can be purchased here. NEW (for me)