Key points are not available for this paper at this time.
Marjorie B. McElroy, Edwin Burmeister, Arbitrage Pricing Theory as a Restricted Nonlinear Multivariate Regression Model: Iterated Nonlinear Seemingly Unrelated Regression Estimates, Journal of Business & Economic Statistics, Vol. 6, No. 1 (Jan., 1988), pp. 29-42
McElroy et al. (Fri,) studied this question.