Received: 4 January 2019
Accepted: 9 April 2019
First Online: 6 May 2019
Ethics approval and consent to participate
: This study was approved by the Ethics Committee of the Centre of Postgraduate Medical Education, Warsaw Poland. (14 November 2015, ref.: 77/PB/2015) The study included written parental informed consent.
: Not applicable.
: The authors declare they have no competing interests.
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