Funding for this research was provided by:
Faculty of Medicine at the Trakia University, Stara Zagora, Bulgaria (Grant no. 8/2016)
Text and Data Mining valid from 2019-03-25
Received: 11 December 2018
Accepted: 15 March 2019
First Online: 25 March 2019
Compliance with ethical standards
: The authors declare that they have no conflict of interest.
: All procedures performed in studies involving human participants were in accordance with the ethical standards of the institutional and/or national research committee and with the 1964 Helsinki declaration and its later amendments or comparable ethical standards. This article does not contain any studies with animals performed by any of the authors.