Observational evidence.
Hennekens
C H
CH
Division of Preventive Medicine, Harvard Medical School, Brigham and Women's Hospital, Boston, MA 02215-1204.
Buring
J E
JE
D000818:Animals; D015982:Bias; D016022:Case-Control Studies; D015331:Cohort Studies; D015986:Confounding Factors, Epidemiologic; D006801:Humans; D016032:Randomized Controlled Trials as Topic; D015203:Reproducibility of Results; D012107:Research Design; D012307:Risk Factors; D016896:Treatment Outcome