Marcel Wolbers and Werner A. Stahel (2005).
Linear Unmixing of Multivariate Observations: A Structural Model.
J. Amer. Statist. Assoc., Dec. 2005 (in print)
Additional material:
Remarks on the paper (pdf)
(postscript)
Werner A. Stahel (1981). Breakdown of Covariance Estimators
Research Report 31, Fachgruppe f. Statistik, ETH Zurich
First report on the estimator known as "Stahel-Donoho estimator"