This entire book can be downloaded here
Tag: Roy Krenkel
Back to the Stone Age: A Castaway in Pellucidar (Original Title: Seven Worlds to Conquer)
Pirates Of Venus (Ace 1963)
Thuvia, Maid of Mars (Ace)
The Master Mind of Mars (1963)
Out Of Time’s Abyss
The Lost Continent’s most startling secret
Tanar of Pellucidar
The Moon Maid
This story was also published in Argosy, with a fantastic cover by P. J. Monahan