Edwin J. Andrews : An Updated Analysis of Poland General Duty Revenue Tax Rates and Effects of Hyperinflation, 1920 - 1924
in: POLONUS 578 - March 2020 Bulletin of the Polish Philatelic Society Benicia, CA 2020

# Polen # Fiskalmarken / Stempelmarken # Inflation

Jerzy W. Kupiec-Weglinski : Polish Mail Flown by Zeppelin Airships
in: POLONUS 578 - March 2020 Bulletin of the Polish Philatelic Society Benicia, CA 2020

# Polen # Zeppelin

Hank Bieniecki : Unlisted Signed Artists Proofs 1947 World of Workers
in: POLONUS 578 - March 2020 Bulletin of the Polish Philatelic Society Benicia, CA 2020

# Polen # Studien zu einzelnen Marken / Markenserien