Bumi Berongga: Perbedaan antara revisi

* Standish, David. ''Hollow Earth : the Long and Curious History of Imagining Strange Lands, Fantastical Creatures, Advanced Civilizations, and Marvelous Machines Below the Earth's Surface''. Da Capo Press, 2006.

* Lamprecht, Jan. ''Hollow Planets: A Feasibility Study of Possible Hollow Worlds'' Grave Distraction Publications, 2014.

 

== Pranala luar ==