article :Britney Spears hits back at lip sync reports insisting she WILL sing live in Las Vegas but admits she 'doesn't sound so great all the time' http://www.dailymail.co.uk/tvshowbiz/article-2446645/Britney-Spears-hits-lip-sync-reports-insisting-WILL-sing-live-Las-Vegas-admits-doesnt-sound-great-time.html#ixzz2gzl2avRZ