First published in Air Trails and Science Frontiers magazine, May 1947 as by "Capt. B. A. Northrop."
| Date | Publication | Publisher | Type | Page | |
|---|---|---|---|---|---|
| November 1957 | Fortress in the Sky | Hubbard Association of Scientologists | Nonfiction | ||
| 1967 | Fortress in the Sky: | Publications Organization World Wide | Nonfiction |