Key points are not available for this paper at this time.
J. Rice, T. Reich, C. R. Cloninger, R. Wette, An Approximation to the Multivariate Normal Integral: Its Application to Multifactorial Qualitative Traits, Biometrics, Vol. 35, No. 2 (Jun., 1979), pp. 451-459
Rice et al. (Fri,) studied this question.