Funding for this research was provided by:
Netherlands organization for Health Research and Development (314030201)
Received: 6 June 2018
Accepted: 18 March 2019
First Online: 1 April 2019
Ethics approval and consent to participate
: The research proposal has been reviewed by the medical ethics committee of Erasmus Medical Centre (study protocol number MEC-2011-197). The committee decided that the rules laid down in the Medical Research Involving Human Subjects Act did not apply. Prior to giving their written consent, all respondents were informed about the aims of the study and its anonymous and voluntary nature.
: Not applicable.
: We have no competing interests.
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