  Unfortunately the proof of the main result of [1], Theorem 1, has a flaw.
Namely, Lemma 13 used in the proof of Proposition 11 is correct only under an
additional assumption that the operator $A$ is normal (adjoint for the
one-sided shift operator in $l^2(\mathbb N)$ provides a counterexample). Below
we prove a version of Lemma 13 that does not require the normality assumption
and apply it to prove Proposition 11. In addition, the same version of the
lemma appears in paper [2] (as Lemma 3.1) where it is used in the proof of
Theorem 1.6. We also explain here how to use the new version of Lemma 13 to
correct the proof of Theorem 1.6 from [2].
