RT Journal Article SR Electronic T1 Pelvic inflammatory disease epidemiology: what do we know and what do we need to know? JF Sexually Transmitted Infections JO Sex Transm Infect FD BMJ Publishing Group Ltd SP 80 OP 87 DO 10.1136/sti.76.2.80 VO 76 IS 2 A1 I Simms A1 J M Stephenson YR 2000 UL http://sti.bmj.com/content/76/2/80.abstract AB