Authors
Dragomir Marchev
Shumen University, Faculty of Natural Sciences, Department of Physics and Astronomy, Shumen, Bulgaria
Georgi Dimitrov
Shumen University, Faculty of Mathematics and Informatics, Department of Computer Informatics, Shumen, Bulgaria
Nataliya Pavlova
Shumen University, Faculty of Mathematics and Informatics, Department of Computer Informatics, Shumen, Bulgaria
Borislav Stoyanov
Shumen University, Faculty of Mathematics and Informatics, Department of Computer Informatics, Shumen, Bulgaria