Wald, N. J., Kennard, A., Densem, J. W., Chard, T., & Butler, L. (1992). Antenatal screening for Down's syndrome.

Wald, N J., A. Kennard, J W. Densem, T. Chard, و L. Butler. Antenatal Screening for Down's Syndrome. 1992.

Wald, N J., et al. Antenatal Screening for Down's Syndrome. 1992.