Berentzen, N E
Smit, H A
van Rossem, L
Gehring, U
Kerkhof, M
Postma, D S
Boshuizen, H C
Wijga, A H
Article History
Received: 20 January 2014
Revised: 19 May 2014
Accepted: 11 June 2014
First Online: 20 June 2014
Competing interests
: The authors declare no conflict of interest.