RT Journal Article SR Electronic T1 US estrogen plus progestin HRT trial stopped due to increased risk of breast cancer, stroke and heart attack JF Canadian Medical Association Journal JO CMAJ FD Canadian Medical Association SP 294 OP 294-a VO 167 IS 3 A1 Barbara Sibbald YR 2002 UL http://www.cmaj.ca/content/167/3/294.2.abstract