RT Journal Article SR Electronic T1 Selecting the sample JF Evidence Based Nursing JO Evid Based Nurs FD BMJ Publishing Group Ltd and RCN Publishing Company Ltd SP 32 OP 33 DO 10.1136/eb-2014-101747 VO 17 IS 2 A1 Allison Shorten A1 Calvin Moorley YR 2014 UL http://ebn.bmj.com/content/17/2/32.abstract AB