Received: 12 April 2017
Accepted: 19 April 2018
First Online: 15 June 2018
Ethics approval and consent to participate
: In collecting the survey data, respondents provided oral consent to be interviewed by telephone or implied consent when proceeding to answer the online questionnaire. Ethical approval was given by the Danish Data Protection Agency (Datatilsynet).
: The authors declare that they have no competing interests.
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