Sirakov, S.
Sirakov, A.
Bhogal, P.
Penkov, M.
Minkin, K.
Ninov, K.
Hristov, H.
Karakostov, V.
Raychev, R.
Article History
Received: 25 April 2019
Accepted: 19 July 2019
First Online: 9 August 2019
Compliance with ethical guidelines
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: S. Sirakov, A. Sirakov, P. Bhogal, M. Penkov, K. Minkin, K. Ninov, H. Hristov, V. Karakostov and R. Raychev declare that they have no competing interests.
: All procedures performed in the 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. Informed consent was obtained from all individual participants included in the study.