Todorova, Teodora
Miteva, Daniela
Chankova, Stephka
Funding for this research was provided by:
National Science Fund, Ministry of Education and Science (DH11/10)
Article History
Received: 2 August 2018
Revised: 3 January 2019
Accepted: 13 February 2019
First Online: 14 March 2019
Compliance with Ethical Standards
:
: The authors declare that they have no conflict of interest.