Received: 22 May 2018
Accepted: 22 January 2019
First Online: 31 January 2019
Ethics approval and consent to participate
: The project was approved by the Opole Voivodship Ethics Committee (resolution no. 202, June 6th, 2013). Signed informed consent was obtained from all tested persons and the rights of subjects were protected.
: Not applicable.
: The authors declare that they have no competing interests.
: Springer Nature remains neutral with regard to jurisdictional claims in published maps and institutional affiliations.