6A framework for development and evaluation of RCTs for complex interventions to improve health.Medical Research Council(MRC).April 2000.Page 3.;http://www.mrc.ac.uk/pm/pdf-mrc-cpr.pdf;http://www.mrc.ac.uk/Utilities/Documentrecord/index.htm?d=MRC003372.
7National Institute for Health and Clinical Excellence(April 2007)‘The guidelines manual'.London:National Institute for Health and Clinical Excellence.http://www.nice.org.uk/media/A75/83/The_guidelines_manual-2009_-_Contents_and_changes_from_2007_manual.pdf.
