Mendes, C. C., J. M. Biselli, B. L. Zampieri, E. M. Goloni-Bertollo, M. N. Eberlin, R. Haddad, M. F. Riccio, H. Vannucchi, V. M. Carvalho, and Érika C. Pavarino-Bertelli. “19-Base Pair Deletion Polymorphism of the Dihydrofolate Reductase (DHFR) Gene: Maternal Risk of Down Syndrome and Folate Metabolism”. São Paulo Medical Journal, vol. 128, no. 4, July 2010, pp. 215-8, https://periodicosapm.emnuvens.com.br/spmj/article/view/1798.