Yotovska, K., and P.-G. Kalou. “Design of a University Course for the Training of Biology Teachers in a Virtual Environment (Analysis of Results Taking into Account Students’ Attitudes to the E-Learning)”. American Scientific Research Journal for Engineering, Technology, and Sciences, vol. 46, no. 1, Aug. 2018, pp. 58-70, https://asrjetsjournal.org/index.php/American_Scientific_Journal/article/view/4320.