WASET
    G. Theonas and  D. Hobbs and  D. Rigas,  The Effect of Facial Expressions on Students in Virtual Educational Environments.   journal   = {International Journal of Educational and Pedagogical Sciences}, [online]. World Academy of Science, Engineering and Technology.
    November 2007, vol. 11(11). 625 - 632
    [viewed 11 May 2024]. Available from: https://publications.waset.org/pdf/3623.