License agreement
For all articles applied the Creative Commons CC-BY license (Attribution). Under the terms of a CC BY license "you must give appropriate credit, provide a link to the license, and indicate if changes were made". "You may do so in any reasonable manner, but not in any way that suggests the licensor endorses you or your use" (from creativecommons.org).
Attention! Unfortunately, when converting the articles to PDF format, an error was made regarding copyright. The information "Copyright © 2021 by author and the journal" is not true, all rights belong to the authors of the article. We are working to fix the information in the PDF files.
Download license agreement docx