@InProceedings{yfh:a151,
   title = {A family of optimally conditioned quasi-Newton updates for unconstrained optimization},
   author = {Y. F. Hu and C. Storey},
   year = 1994,
   BookTitle = {Journal of Optimization Theory and Applications},
   att_url = {http://www2.research.att.com/areas/visualization/papers_videos/pdf/yfh-a151.pdf}
}