Download the full article as a PDF file.
© 2022 Dragomir Marchev, Kiril Stoyanov, Vladislav Marchev, Radoslav Zamanov, Borislav Borisov, Doroteq Vasileva, Teodora Atanasova, Nataliya Pavlova, published by Konstantin Preslavski University of Shumen
This work is licensed under the Creative Commons Attribution 3.0 License.