Ace Science Fiction Classic Pocket Paperbacks

Edgar Rice Burroughs published between 1912 (The Princess of Mars) and his last novel (Savage Pellucidar) issued in 1963 after his death in 1950

The People That Time Forgot, first published 1918, cover by Roy Krenkel Jnr

The Moon Men  and The Red Hawk, first published 1923, cover by Ed Emsh

The Moon Maid, first published 1925, cover by Frank Frazetta