This book contains many accounts of people being found inside the earth via the North Pole but mainly stories of people having gone there via tunnels, it seems known in Buddhism as tunnels connect the surface to the inside the earth and there are also testimonies of people who saw these people on the surface, as sometimes they seem to come to the surface and pay old unknown currency. There is also reference books and other extracts talking in more detail and also some surprises as the story of a sailor who found off the Brittany town under the ocean after research on his part would be the paris sister city buried under the ocean ...
Personally, I think these testimonies mostly true, otherwise why do we never see satellite photo of poles that have artificially added black hole and we are told that it is the satellite that has not able to collect data at that location? We could map the planets as March, but not the land on poles! Get serious does not hurt. It appears also that no commercial plane will fly over the poles, officially because of possible disruption ...