"HubbleSite: Black Holes: Gravity's Relentless Pull Interactive: Encyclopedia." HubbleSite: Black Holes: Gravity's Relentless Pull Interactive: Encyclopedia. Web. 13 Apr. 2015. <http://hubblesite.org/explore_astronomy/black_holes/encyc_mod3_q2.html>.
"Is Time Travel Possible?| Explore | Physics.org." Is Time Travel Possible?| Explore | Physics.org. Web. 13 Apr. 2015. <http://www.physics.org/article-questions.asp?id=131>.
"Physicists Achieve Quantum Teleportation of Photon Over 25 Kilometers." IFLScience. 22 Sept. 2014. Web. 13 Apr. 2015. <http://www.iflscience.com/physics/physicists-achieve-quantum-teleportation-photon-over-25-kilometers>.
"Space and Time Warps - Stephen Hawking." Space and Time Warps - Stephen Hawking. Web. 17 Apr. 2015. <http://www.hawking.org.uk/space-and-time-warps.html>.
"Event Horizon | Black Hole." Encyclopedia Britannica Online. Encyclopedia Britannica. Web. 13 Apr. 2015. <http://www.britannica.com/EBchecked/topic/197134/event-horizon>.
Knight, Randall Dewey. Physics for Scientists and Engineers: A Strategic Approach. San Francisco: Pearson/Addison Wesley, 2004. Print.