Correction to "An invalid norm appearing in control and estimation"

Two counterexamples are presented in the above correspondence [1] to demonstrate that
\|A\|_{3}
,the minimum of the standard column-sum norm
(\|A\|_{1})
and the row-sum norm
(\|A\|_{2})
, is not a valid norm. While these observations are correct, there is an error in [1] in the argument used to justify the use of
\|A\|_{3}
as a convergence test. This error is corrected here.