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2. Statista: Number of available apps in the Apple App Store from July 2008 to January 2017 (2017). https://www.statista.com/statistics/263795/number-of-available-apps-in-the-apple-app-store/ . Accessed Aug 2017
3. Statista: Number of available applications in the Google Play Store from December 2009 to June 2017 (2017). https://www.statista.com/statistics/266210/number-of-available-applications-in-the-google-play-store/ . Accessed Aug 2017
4. Statista: Number of available apps in the Amazon Appstore from March 2011 to April 2016 (2017). https://www.statista.com/statistics/307330/number-of-available-apps-in-the-amazon-appstore/ . Accessed Aug 2017
5. Check Point: Viking horde: a new type of android malware on Google Play (2017). https://blog.checkpoint.com/2016/05/09/viking-horde-a-new-type-of-android-malware-on-google-play/ . Accessed Aug 2017