RT Journal Article SR Electronic T1 Population ideals and sample realities—why we still need access to comprehensive information about populations JF Journal of Epidemiology and Community Health JO J Epidemiol Community Health FD BMJ Publishing Group Ltd SP 257 OP 257 DO 10.1136/jech.2004.028753 VO 59 IS 4 A1 Geraldine Barrett A1 Janet L Peacock YR 2005 UL http://jech.bmj.com/content/59/4/257.abstract AB