Keogh-Brown, M; Bachmann, M; Shepstone, L; Hewitt, C; Howe, A; Ramsay, C; Song, F; Miles, J; Torgerson, D; Miles, S; +3 more... Elbourne, D; Harvey, I; Campbell, M; (2007) Contamination in trials of educational interventions. Health technology assessment (Winchester, England), 11 (43). 1-+. ISSN 1366-5278 https://researchonline.lshtm.ac.uk/id/eprint/6318