6Share of U.S. online population who have used smartphone, tablet or e-reader to take online classes or tutorials as of January 2014, by age[EB/OL].http://www.statista.com/statistics/334055/us-mobile- online-classes-and-tutorial-reach-age/,2016-02-10.
9MathsEverywhere.Country Profile: United Kingdom Of Great Britain and Northern Ireland[EB/OL]. http://www.unesco.org/uil/ litbase/?menu=4&programme= 174, 2016-02-10.
10IU center awarded Library of Congress grant for educational app development[EB/OL].http://news.indiana.edu/releases/iu/2015/10/ representative-government-grant.shtml,2016-02-10.