[The Caves of Steel Doubleday first publication cover]. {n.d.). Retrieved from http://en.wikipedia.org/wiki/The_caves_of_steel
[The Lathe of Heaven SF Masterworks cover]. (2010, August 25). Retrieved from http://solarbridge.wordpress.com/2010/08/25/the-lathe-of-heaven-ursula-le-guin-sf-masterworks/
[We Penguin edition cover]. (1980). Retrieved from http://seducedbystarlight.blogspot.com/2012/07/two-covers-we-by-yevgeny-zamyatin.html
[Portal 2 multiplayer cover]. (2011, April 19). Retrieved from http://half-life.wikia.com/wiki/Portal_2
[We Penguin Classics cover]. (n.d.). Retrieved from http://thephilosopherscabin.blogspot.com/2012/02/we.html
[Giskard cover from The Robots of Dawn]. (n.d.). Retrieved from http://4.bp.blogspot.com/-KsIHueiRmbc/T4HFTnHlJ8I/AAAAAAAAAJg/zyoa_R6uOxE/s1600/Sin+t%25C3%25ADstulo.jpg
(etc.)