エドガー・ライス・バローズ

At the Earth's Core is a 1914 fantasy novel by Edgar Rice Burroughs, the first in his series about the fictional "hollow earth" land of Pellucidar. It first appeared as a four-part serial in All-Story Weekly from April 4–25, 1914. It was first published in book form in hardcover by A. C. McClurg in July, 1922.

Back to the Stone Age is a novel written by Edgar Rice Burroughs, the fifth in his series set in the interior world of Pellucidar. It first appeared as a six-part serial in Argosy Weekly from January 9 to February 13, 1937 under the title "Seven Worlds to Conquer." It was first published in book form in hardcover by …