
Download the full article as a PDF file.
© 2016 Lyubomir Ts. Beshev, Angel P. Marinov, Tihomir V. Andreev, Nachko I. Totzev, Valentin Ch. Velikov, Tsvetomir G. Georgiev, Angel S. Grigorov, Boris D. Tsankov, Borislav A. Ignatov, published by Sciendo
This work is licensed under the Creative Commons Attribution-NonCommercial-NoDerivatives 4.0 License.