Ethical and policy issues in cluster randomized trials: rationale and design of a mixed methods research study. by Taljaard, M, Weijer, C, Grimshaw, J, Belle Brown, J, Binik, A, Boruch, R, Brehaut, J, Chaudhry, S, Eccles, M, McRae, A, Saginur, R, Zwarenstein, M, Donner, A