@article {BobrVava2,
	title = {Accurate Solution of Weighted Least Squares by Iterative Methods},
	journal = {SIAM J. Matrix Anal. App.},
	volume = {22},
	year = {2001},
	pages = {1153-1174},
	author = {E. Y. Bobrovnikova and S. A. Vavasis}
}
