1.   A recent overview, which includes all case control studies, reports a highly significant duration-related effect of early OC use on premenopausal breast cancer.

2.   In what is known as a case control study, health workers will compare the therapies given to those who survived and those who died.

3.   The American Health Foundation used a different kind of scientific tool known as case control studies.

4.   The design of case control studies, looking at past events, generally prevents definitive conclusions.

5.   The study was of a type that epidemiologists call a case control study.

6.   The study was a type known as case control.

7.   The CDC experts had hoped to release preliminary findings on a case control study before leaving Hong Kong.