Methylenetetrahydrofolate reductase polymorphism, plasma folate, homocysteine and risk of myocardial infarction in US physicians. - Ma, J; Stampfer, MJ; Hennekens, CH; Frosst, P; Selhub, J; Horsford, J; Malinow, M; Willett, WC; Rozen, R (Circulation, 1996)