References
- Subnormal operators J. B. Conway
- Ph.D. thesis, Indiana University Subscalar and quasisubscalar operators Eungil Ko
- J. Operator Theory v.12 Hyponormal operators are subscalar M. Putinar
- Invariant subspaces H. Radjavi;P. Rosenthal
Let $H$ and $K$ be separable, complex Hilbert spaces and $L(H, K)$ denote the space of all linear, bounded operators from $H$ to $K$. If $H = K$, we write $L(H)$ in place of $L(H, K)$. An operator $T$ in $L(H)$ is called hyponormal if $TT^* \leq T^*T$, or equivalently, if $\left\