The Hollow Earth: The Greatest Geographical Discovery in History Made by Admiral Richard E. Byrd in the Mysterious Land Beyond the Poles- The True Origin of the Flying Saucers by Raymond W Bernard (PDF)
The author claims that this book proves that there exists on the inside of the earth's crust, which is about 800 miles thick, a New World, and that Admiral Byrd's polar expeditions penetrated a total distance of 4,000 miles into this land beyond the North and South Poles, where there exist immense openings leading to the subterranean world in the hollow interior of the earth, home of a super race and super civilization, who are the creators of the flying saucers.

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