RT Journal Article SR Electronic T1 Control Charts for the Standard Mortality Ratio JF British Journal of Social Medicine JO Br J Soc Med FD BMJ Publishing Group Ltd SP 69 OP 76 DO 10.1136/jech.3.2.69 VO 3 IS 2 A1 Herdan, G. YR 1949 UL http://jech.bmj.com/content/3/2/69.abstract AB