9Koller D,Andrew N,Do C,et al. Retention and In- tention in Massive Open Online Courses: In Depth [EB/OL]. [2014 - 01 - 22]. http://www. educause. edu/ero/article/.
10Ho A D, Reich J, Nesterko S O, et al. HarvardX and MITx:The First Year of Open Online Courses, Fall 2012-Summer 2013[EB/OL]. [2014 - 01 - 21]. http://papers. ssm. com/abstract= 2381263.