A. Donner and N. Klar, Design and Analysis of Cluster Randomization Trials in Health Research London, 2000.

D. Murray, Design and Analysis of Group-Randomized Trials, 1998.

R. Reading, I. Harvey, and M. Mclean, Cluster randomised trials in maternal and child health: implications for power and sample size, Archives of Disease in Childhood, vol.82, issue.1, pp.79-83, 2000.
DOI : 10.1136/adc.82.1.79

D. Murray, S. Varnell, and J. Blitstein, Design and Analysis of Group-Randomized Trials: A Review of Recent Methodological Developments, American Journal of Public Health, vol.94, issue.3, pp.423-432, 2004.
DOI : 10.2105/AJPH.94.3.423

A. Donner and N. Klar, Pitfalls of and Controversies in Cluster Randomization Trials, American Journal of Public Health, vol.94, issue.3, pp.416-422, 2004.
DOI : 10.2105/AJPH.94.3.416

S. Eldridge, D. Ashby, G. Feder, A. Rudnicka, and O. Ukoumunne, Lessons for cluster randomized trials in the twenty-first century: a systematic review of trials in primary care, Clinical Trials, vol.1, issue.1, pp.80-90, 2004.
DOI : 10.1191/1740774504cn006rr

J. Bland, Cluster randomised trials in the medical literature: two bibliometric surveys, BMC Medical Research Methodology, vol.328, issue.1, p.21, 2004.
DOI : 10.1136/bmj.328.7441.702

S. Kerry and J. Bland, Statistics notes: Sample size in cluster randomisation, BMJ, vol.316, issue.7130, p.549, 1998.
DOI : 10.1136/bmj.316.7130.549
URL : http://www.bmj.com/cgi/content/short/316/7130/549

G. Adams, M. Gulliford, O. Ukoumunne, S. Eldridge, S. Chinn et al., Patterns of intra-cluster correlation from primary care research to inform study design and analysis, Journal of Clinical Epidemiology, vol.57, issue.8, pp.785-794, 2004.
DOI : 10.1016/j.jclinepi.2003.12.013

R. Turner, A. Prevost, and S. Thompson, Allowing for imprecision of the intracluster correlation coefficient in the design of cluster randomized trials, Statistics in Medicine, vol.21, issue.8, pp.1195-1214, 2004.
DOI : 10.1002/sim.1721

S. Lake, E. Kammann, N. Klar, and R. Betensky, Sample size re-estimation in cluster randomization trials, Statistics in Medicine, vol.1, issue.10, pp.1337-1350, 2002.
DOI : 10.1002/sim.1121

O. Ukoumunne, M. Gulliford, C. Chinn, J. Sterne, and P. Burney, Methods for evaluating area-wide and organisation-based interventions in health and health care: a systematic review, Health Technology Assessment, vol.3, p.92, 1999.

O. Ukoumunne, M. Gulliford, S. Chinn, J. Sterne, P. Burney et al., Methods in health service research: Evaluation of health interventions at area and organisation level, BMJ, vol.319, issue.7206, pp.376-379, 1999.
DOI : 10.1136/bmj.319.7206.376

T. Flynn, E. Whitley, and T. Peters, Recruitment strategies in a cluster randomized trial - cost implications, Statistics in Medicine, vol.13, issue.3, pp.397-405, 2002.
DOI : 10.1002/sim.1025

M. Campbell, S. Thomson, C. Ramsay, G. Maclennan, and J. Grimshaw, Sample size calculator for cluster randomized trials, Computers in Biology and Medicine, vol.34, issue.2, pp.113-138, 2004.
DOI : 10.1016/S0010-4825(03)00039-8

M. Gulliford, G. Adams, O. Ukoumunne, R. Latinovic, S. Chinn et al., Intraclass correlation coefficient and outcome prevalence are associated in clustered binary data, Journal of Clinical Epidemiology, vol.58, issue.3, pp.246-251, 2005.
DOI : 10.1016/j.jclinepi.2004.08.012

P. Hannan, D. Murray, and R. David, PARAMETERS TO AID IN THE DESIGN AND ANALYSIS OF COMMUNITY TRIALS, Epidemiology, vol.5, issue.1, pp.88-95, 1994.
DOI : 10.1097/00001648-199401000-00013

O. Siddiqui, D. Hedeker, B. Flay, and F. Hu, Intraclass Correlation Estimates in a School-based Smoking Prevention Study: Outcome and Mediating Variables, by Sex and Ethnicity, American Journal of Epidemiology, vol.144, issue.4, pp.425-433, 1996.
DOI : 10.1093/oxfordjournals.aje.a008945

L. Smeeth, S. Ng, and E. , Intraclass correlation coefficients for cluster randomized trials in primary care, Controlled Clinical Trials, vol.23, issue.4, pp.409-421, 2002.
DOI : 10.1016/S0197-2456(02)00208-8

B. Martinson, D. Murray, R. Jeffery, and D. Hennrikus, Intraclass Correlation for Measures from a Worksite Health Promotion Study: Estimates, Correlates, and Applications, American Journal of Health Promotion, vol.13, issue.6, pp.347-357, 1999.
DOI : 10.4278/0890-1171-13.6.347

D. Murray, G. Phillips, A. Birnbaum, and L. Lytle, Intraclass Correlation for Measures from a Middle School Nutrition Intervention Study: Estimates, Correlates, and Applications, Health Education & Behavior, vol.28, issue.6, pp.666-679, 2001.
DOI : 10.1177/109019810102800602

D. Murray, M. Clark, and C. Alexander, Intraclass correlations from a community-based alcohol prevention study: the effect of repeat observations on the same communities., Journal of Studies on Alcohol, vol.61, issue.6, pp.881-890, 2000.
DOI : 10.15288/jsa.2000.61.881

D. Murray and B. Short, Intraclass correlation among measures related to tobacco use by adolescents: Estimates, correlates, and applications in intervention studies, Addictive Behaviors, vol.22, issue.1, pp.1-12, 1997.
DOI : 10.1016/0306-4603(95)00099-2

A. Donner and N. Klar, Statistical considerations in the design and analysis of community intervention trials, Journal of Clinical Epidemiology, vol.49, issue.4, pp.435-439, 1996.
DOI : 10.1016/0895-4356(95)00511-0

A. Manatunga, M. Hudgens, and S. Chen, Sample Size Estimation in Cluster Randomized Studies with Varying Cluster Size, Biometrical Journal, vol.77, issue.1, pp.75-86, 2001.
DOI : 10.1002/1521-4036(200102)43:1<75::AID-BIMJ75>3.0.CO;2-N

S. Kerry and J. Bland, Unequal cluster sizes for trials in English and Welsh general practice: implications for sample size calculations, Statistics in Medicine, vol.78, issue.3, pp.377-390, 2001.
DOI : 10.1002/1097-0258(20010215)20:3<377::AID-SIM799>3.0.CO;2-N

A. Donner, Some aspects of the design and analysis of cluster randomization trials, Journal of the Royal Statistical Society: Series C (Applied Statistics), vol.47, issue.1, pp.95-113, 1998.
DOI : 10.1111/1467-9876.00100

L. Moore, R. Campbell, A. Whelan, N. Mills, P. Lupton et al., Self help smoking cessation in pregnancy: cluster randomised controlled trial, BMJ, vol.325, issue.7377, pp.1383-1388, 2002.
DOI : 10.1136/bmj.325.7377.1383
URL : http://www.ncbi.nlm.nih.gov/pmc/articles/PMC138509

D. Murray, S. Mckinlay, D. Martin, A. Donner, J. Dwyer et al., Design and Analysis Issues in Community Trials, Evaluation Review, vol.18, issue.4, pp.493-514, 1994.
DOI : 10.1177/0193841X9401800407

M. Campbell, D. Elbourne, and D. Altman, CONSORT statement: extension to cluster randomised trials, BMJ, vol.328, issue.7441, pp.702-708, 2004.
DOI : 10.1136/bmj.328.7441.702
URL : http://www.ncbi.nlm.nih.gov/pmc/articles/PMC381234

D. Elbourne and M. Campbell, Extending the CONSORT statement to cluster randomized trials: for discussion, Statistics in Medicine, vol.319, issue.3, pp.489-496, 2001.
DOI : 10.1002/1097-0258(20010215)20:3<489::AID-SIM806>3.0.CO;2-S

M. Campbell, J. Grimshaw, and D. Elbourne, Intracluster correlation coefficients in cluster randomized trials: empirical insights into how should they be reported, BMC Medical Research Methodology, vol.285, issue.5, p.9, 2004.
DOI : 10.1001/jama.285.15.1996