Fraser, D M
Sullivan, F M
Thompson, A M
McCowan, C
Article History
Received: 10 January 2014
Revised: 6 April 2014
Accepted: 24 April 2014
First Online: 19 June 2014
Competing interests
: All authors have completed the ICMJE uniform disclosure form at ExternalRef removed; none of the authors have financial relationships with any organisations that might have an interest in the submitted work in the previous 3 years and have no other relationships or activities that could appear to have influenced the submitted work.