Letter (Astounding, February 1939): Concerning "Gravity Plates."
From Author Wars - https://authorwars.com/books/letter-astounding-february-1939-concerning-gravity-plates-2091880.html
Overview:
Editions/Publications:
- Unknown. Astounding Science-Fiction, February 1939 (Unknown, Willy Ley, Street & Smith Publications, Inc., $0.20, 164 pages, pulp, MAGAZINE)