A reprint appears in Int J Nurs Stud. 2013 May;50(5):587-92.
A comment on this article appears in "New MRC guidance on evaluating complex interventions." BMJ. 2008;337:a1937.
A comment on this article appears in "Assessing complex interventions. Guidelines perpetuate inappropriate methods." BMJ. 2008;337:a2473.

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