1. Tricks or treats with the Hilbert matrix;Choi;Amer. Math. Monthly,1983
2. G. Corach, H. Porta, and L. Recht, The geometry of the space of self-adjoint invertible elements of a Cast;-algebra, to appear.
3. G. Corach, H. Porta, and L. Recht, The geometry of spaces of projections in Cast;-algebras, Adv. in Math., to appear.
4. The norm of the Schur product operation;Davis;Numer. Math.,1962
5. Aufgaben und Lehrsätze;Pólya,1925