Optimal Adaptive Control: A Multivariate Model for Marketing Applications." Little, John D.C. IEEE Transactions on Automatic Control Vol. 22, No. 2 (1977): 187-195.
Robust Regression Using Iteratively Re-weighted Least-Squares." Holland, Paul and Roy E. Welsch. Communications in Statistics, Part A Vol. 6, No. 9 (1977): 813-827.