Text and Data Mining valid from 2018-04-16
Received: 9 October 2017
Accepted: 10 April 2018
First Online: 16 April 2018
Ethics approval and the consent to participate
: The study was approved by the Regional Committee for Medical and Health Research Ethics (REK South-East), Norway, and written consent was given by the study participants.
: The authors declare that they have no competing interests.
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