@article {pierrakeas2003evaluating, title = {Evaluating and improving educational material and tutoring aspects of distance learning systems}, journal = {Studies in Educational Evaluation}, volume = {29}, number = {4}, year = {2003}, pages = {335{\textendash}349}, publisher = {Pergamon}, author = {Christos J. Pierrakeas and Xenos, Michalis and Pintelas, Panayiotis} }