Gene-gene interaction between the cystathionine beta-synthase 31 base pair variable number of tandem repeats and the methylenetetrahydrofolate reductase 677C > T polymorphism on homocysteine levels and risk for neural tube defects - Afman,L.A.; Lievers,K.J.; Kluijtmans,L.A.; Trijbels,F.J.; Blom,H.J. (Mol Genet Metab, 2003)