Funding for this research was provided by:
Berufsgenossenschaft für Transport und Verkehrswirtschaft (“BG Verkehr”), Hamburg (N/A)
Received: 12 January 2019
Accepted: 2 April 2019
First Online: 11 April 2019
Ethics approval and consent to participate
: Taking part in this study was voluntarily. All participants gave their informed consent before taking part in this study. The study was approved by the Ethics Committee of the Hamburg Medical Association (no PV4395).
: Not applicable.
: The authors declare that they have no competing interests.
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