Admiral Byrd mission: last survivor speaks

(UNITY) Admiral Richard Evelyn Byrd Jr. wrote a diary that was replaced by the CIA (or its predecessor organization OSS) then hidden away until, possibly, his son released the real, unredacted original version after his father's passing. It recounts what Byrd found -- a very advanced civilization living in Agartha (our Hollow Earth) as spoken of in Hindu and Buddhist texts. The momentous mission was Operation Highjump (about The Secret Land)