Popova, Velichka http://orcid.org/0000-0001-5733-5520
Vazhev, Zaprin http://orcid.org/0000-0003-3344-4444
Geneva-Popova, Mariela http://orcid.org/0000-0002-7655-3846
Batalov, Anastas http://orcid.org/0000-0001-8857-0574
Article History
Received: 6 May 2019
Accepted: 1 July 2019
First Online: 11 July 2019
Compliance with ethical standards
:
: All procedures were conducted in accordance with the WMA Declaration of Helsinki (1964) and approved by the local research ethics committee at the Medical University in Plovdiv.
: All authors declare that they have no conflict of interest.
: Informed consent was obtained from each participant involved in this research.