van Boven, Job FM
Trappenburg, Jaap CA
van der Molen, Thys
Chavannes, Niels H
Article History
Received: 24 November 2014
Revised: 31 May 2015
Accepted: 1 June 2015
First Online: 16 July 2015
Competing interests
: NHC is an Associate Editor of <i>npj Primary Care Respiratory Medicine</i>, but was not involved in the editorial review of, nor the decision to publish, this article. The other authors declare no conflict of interest.