Anderson, Gina, and Jan Wittry. "Demonstration Proves Nuclear Fission System Can Provide Space Exploration Power." NASA, 2 May 2018, www.nasa.gov/press-release/demonstration-proves-nuclear-fission-system-can-provide-space-exploration-power.
Cowley, S. C. "The Quest for Fusion Power." Nature Physics 12, 2016.
Meshik, Alex P. "The Workings of an Ancient Nuclear Reactor." Scientific American, 26 Jan. 2009, www.scientificamerican.com/article/ancient-nuclear-reactor/.