Ilieva, Galina http://orcid.org/0000-0001-7504-8576
Yankova, Tania http://orcid.org/0000-0001-5877-3098
Klisarova-Belcheva, Stanislava
Funding for this research was provided by:
Plovdiv University "Paisii Hilendarski" (06-2017)
Article History
Received: 3 December 2017
Revised: 9 May 2018
Accepted: 15 May 2018
First Online: 1 June 2018
Compliance with ethical standards
:
: The authors declare that they have no conflict of interest.