Kayani Mahaz, Aslam Arif M
Lancashire Teaching Hospitals NHS Foundation Trust, Royal Preston Hospital, Fulwood, Preston PR2 9HT, UK.
St Helens and Knowsley Teaching Hospitals NHS Trust, St Helens WA9 3DA, UK
BMJ. 2017 Jun 8;357:j2169. doi: 10.1136/bmj.j2169.