@article {pierrakeas2004comparative, title = {A comparative study of dropout rates and causes for two different distance education courses}, journal = {The International Review of Research in Open and Distributed Learning}, volume = {5}, number = {2}, year = {2004}, author = {Christos J. Pierrakeas and Xeno, Michalis and Panagiotakopoulos, Christos and Vergidis, Dimitris} }