2012 [ edit ] References ^ Marcus, Bennett (June 15, 2011). "Ke$ha Tells Vulture Why She Gave a Hit Song Away to Britney Spears" . New York (New York Media Holdings) . http://nymag.com/daily/entertainment/2011/06/keha_explains_why_she_gave_suc.html . Retrieved September 24, 2011 .   ^ a b (liner notes). "Femme Fatale". Britney Spears .   ^