Burdzhiev, Nikola T.
Baramov, Todor I.
Stanoeva, Elena R.
Yanev, Stanislav G.
Stoyanova, Tsveta D.
Dimitrova, Diana H.
Kostadinova, Kristina A.
Funding for this research was provided by:
National Science Fund of Bulgaria at the Ministry of Education and Science (TK-X-1706/07, DO-02-82/2008)
Sofia University ?St. Kliment Ohridski? (project 80-10-190/26.04.2018)
Article History
Received: 29 June 2018
Accepted: 26 December 2018
First Online: 9 January 2019
Compliance with ethical standards
:
: The authors declare no conflict of interests.