1. The unitary equivalence of binormal operators;Brown;Am. J. Math.,1954
2. Sums of operators with square zero;Fillmore;Acta Sci. Math. (Szeged),1967
3. Products of symmetries;Halmos;Bull. Am. Math. Soc.,1958
4. Sums of small numbers of idempotents;Pearcy;Mich. Math. J.,1967
5. Sums of projections;Stampfli;Duke Math. J.,1964