| Year: | 1976 |
| Author: | Warren SMITH |
| Title: | THE HIDDEN SECRETS OF THE HOLLOW EARTH |
| Language: | English |
| ||
| Year: | 1976 | |
| Publisher: | Zebra, New York | |
 |
| Cover | Title | Year |
|---|---|---|
 |
LET'S FACE THE FACTS ABOUT FLYING SAUCERS |
1967 |
 |
UFO TREK |
1976 |
 |
ANCIENT MYSTERIES OF THE MEXICAN AND MAYAN PYRAMIDS |
1977 |
 |
THIS HOLLOW EARTH |
1977 |