Authors
Vanya Vasileva
University of Shumen Bishop Konstantin Preslavski, Faculty of Natural Sciences, Shumen, Bulgaria
Dora Kabakchieva
University of Shumen Bishop Konstantin Preslavski, Faculty of Natural Sciences, Shumen, Bulgaria
Sevdzhan Sabrieva
University of Shumen Bishop Konstantin Preslavski, Department for Information Qualification and Lifelong Learning, Shumen, Bulgaria
Dimitar Vladev
University of Shumen Bishop Konstantin Preslavski, Faculty of Natural Sciences, Shumen, Bulgaria