6Park, J. -H. , & Choi, H. J. (2009). Factors influencing adult learners'decision to drop out or persist in online learnin. [ J ]. Educational Technology & Society, (4) : 208.
7Royal, A.P. (2003). In search of higher persistence rates in distance education online Programs [ J ]. Internet and Higher Education, (6) : 7.
8Tyler-Smith, K. (2006). Early attrition among first time elearners: A review of factors that contribute to drop-out, withdrawal andnon-completion rates of adult learners undertaking eLeaming programmes [ J]. Journal of Online Learning and Teaching, (2) :74.
