The Hollow Earth by Dr. Raymond Bernard
1968, No Stated Printing, Paperback.
Good. No markings. Front cover has light scratch mark.
"Dr. Raymond Bernard... says that the true home
of the flying saucers is a huge underground world
whose entrance is at the North Polar opening. Dr.
Bernard believes that in the hollow interior of the
earth lives a super-race which wants nothing to do
with man on the surface."