RT Journal Article SR Electronic T1 Improving estimation of the variance of expectation of life for small populations JF Journal of Epidemiology and Community Health JO J Epidemiol Community Health FD BMJ Publishing Group Ltd SP 611 OP 612 DO 10.1136/jech.2003.011338 VO 58 IS 7 A1 Silcocks, P B S YR 2004 UL http://jech.bmj.com/content/58/7/611.abstract AB