- Correspondence to Jan Hovanec, Institute for Prevention and Occupational Medicine of the German Social Accident, Insurance, Institute of the Ruhr University Bochum (IPA), Bochum D-44789, Germany;
- Received November 30, 2018
- Revised February 8, 2019
- Accepted February 10, 2019
- First published February 25, 2019.
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