// <I>WCETR<D> : World conference on ''Educational technology researches'', Nicosia, Cyprus, 2011 : Proc., 28, 2011, p. 739-742 (Book series: Procedia social and behavioral sciences).
T. Stefanova; S. Nunev; B. Todorova;
I. Serbezova;
D. P. Georgieva;
K. Zaharieva;
K. Velcheva и др.