- Author: Frank Scully Daniel Fry Edward Ruppelt Donald Keyhoe
- Language: English
- Year: 2018
- Author: Donald Keyhoe
- Language: English
- Author: Donald Keyhoe
- Language: French
- Year: 1975
- Author: Donald Keyhoe
- Language: English
- Author: Donald Keyhoe
- Language: English
- Author: Donald Keyhoe
- Language: English
- Author: Donald Keyhoe
- Language: English
- Author: Donald Keyhoe
- Language: English
- Year: 2004
- Author: Donald Keyhoe Gordon I R Lore (Jr).
- Language: English
- Year: 1969
- Author: Donald Keyhoe
- Language: English
- Year: 2004