Text and Data Mining valid from 2018-07-30
Received: 10 January 2018
Accepted: 19 July 2018
First Online: 30 July 2018
Compliance with ethical standards
: The study was approved by the Ethics Committee of the Medical University of Bialystok, Poland. Informed consent was obtained from the parents.
: On behalf of all authors, the corresponding author states that there is no conflict of interest.