Proinov, Petko D. http://orcid.org/0000-0002-7057-3010
Petkova, Milena D.
Funding for this research was provided by:
National Science Fund of the Bulgarian Ministry of Education and Science (DN 12-12)
Article History
Received: 17 June 2019
Revised: 3 December 2019
Accepted: 3 June 2020
First Online: 22 June 2020