Schmidt, S A J
Sørensen, G V
Horváth-Puhó, E
Pedersen, L
Obel, N
Petersen, K L
Schønheyder, H C
Sørensen, H T
Article History
Received: 12 December 2014
Revised: 9 March 2015
Accepted: 17 March 2015
First Online: 16 April 2015
Competing interests
: The authors declare no conflict of interest.