1. Tern sets new course with 39 Steps game;39 Steps was first published in 1915 and, therefore, its copyright period is over. 74 As noted in Farber,2007
2. Facebook takes a 30% cut of sales of Facebook credits;See Helft, Miguel,2010
3. Amazon's Disruptive Android App Store Now Open To Developers -Full Details;Andrew Johnson;Financial Times,2011
4. E-business models and consumer expectations for digital audio distribution;Michael Amberg;Journal of Enterprise Information Management,2007