HigHurtenflurst on 15 August 2014
Whoever wrote the textbook seems to be a bit lenient with their sources though, the 2nd pic has sales info for PS3 & X360 sourced from a 1up news article (which would have had to have it's own source link which the textbook author didn't bother to follow)
Then again I guess a maths textbook doesn't really need concrete sources as it's just to get some random numbers that make maths more interesting to the students.
