John Eric Holmes was an American professor of neurology and writer of non-fiction, fantasy and science fiction. His writings appeared under his full name and under variants such as Eric Holmes and J. Eric Holmes and the pen name Sidney Leland.

Pellucidar is a fictional Hollow Earth invented by American writer Edgar Rice Burroughs for a series of action adventure stories. In a crossover event, Tarzan, who was also created by Burroughs, visits Pellucidar.