RT Journal Article SR Electronic T1 Multilevel analytical approaches in social epidemiology: measures of health variation compared with traditional measures of association JF Journal of Epidemiology and Community Health JO J Epidemiol Community Health FD BMJ Publishing Group Ltd SP 550 OP 552 DO 10.1136/jech.57.8.550 VO 57 IS 8 A1 Merlo, J YR 2003 UL http://jech.bmj.com/content/57/8/550.abstract AB