Text and Data Mining valid from 2018-04-03
Received: 11 December 2017
Accepted: 23 March 2018
First Online: 3 April 2018
Ethics approval and consent to participate
: The project proposal has been approved by Regional Committee for Ethics in Medical Research (South-East Norway) with the registration number 2014/2050.A written informed consent will be obtained from all participants included in the analyses, and the project is conducted according to the World Medical Association Declaration of Helsinki.
: Not applicable
: The authors declare that they have no competing interests.
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