If there is an injective compact operator in ; then the operators can be simultaneously diagonalized. (en)
Suppose all the operators in are compact. Then every closed non-zero -invariant sub-space has a common eigenvector for . (en)
If H a finite-dimensional Hilbert space, and a commutative set of operators, each of which is diagonalisable; then the operators can be simultaneously diagonalized. (en)
If all the operators in are compact then the operators can be simultaneously diagonalized. (en)