Georgiev, Tsvetoslav http://orcid.org/0000-0002-1652-4648
Angelov, Alexander Krasimirov http://orcid.org/0000-0003-3062-9478
Article History
Received: 20 February 2019
Accepted: 19 March 2019
First Online: 25 March 2019
Compliance with ethical standards
:
: The authors declare that there is no conflict of interest regarding the publication of this article.
: This article does not contain any studies with human participants or animals performed by any of the authors.