Botto, L. D., Lisi, A., Robert-Gnansia, E., Erickson, J. D., Vollset, S. E., Mastroiacovo, P., Botting, B., Cocchi, G., de Vigan, C., de Walle, H., Feijoo, M., Irgens, L. M., McDonnell, B., Merlob, P., Ritvanen, A., Scarano, G., Siffel, C., Metneki, J., Stoll, C., Smithells, R., & Goujard, J. (2005). international retrospective cohort study of neural tube defects in relation to folic acid recommendations: are the recommendations working?. BMJ, 330(7491), 571–. http://access.bl.uk/ark:/81055/vdc_100177566390.0x00002e