 In "Maps of the Ancient Sea Kings", he reproduces letters that he states he received from the chief of a U.S. Air Force cartography section stationed at Westover AFB in 1961.These letters say that at Hapgood's request, they had studied both Piri Reis and Oronce Finé maps during their off-duty hours, concluding that both were compiled from original source maps of Antarctica at a time when it was relatively free of ice, supporting Hapgood's findings.Hapgood concluded that advanced cartographic knowledge appears on the Piri Reis map and the Oronteus Finaeus map, and must be the result of some unknown ancient civilization that developed advanced scientific knowledge before other civilizations such as Greece.