  The study published in IJMPD 27(4):1850040, 2018 provided a numerical result
for the frequency-shift of GWs due to dispersion in interstellar medium. In
order to adjust the metric functions of the originally improperly matched
`background' spacetime in sections 2.1, the authors have adopted
Darmois--Israel junction conditions. In section 4.1 the code used in the
original paper erroneously computed the magnitude of frequency-shift for the
transient event GW150914 due to a missing conversion factor. In both cases
where numerical errors and potential contradictions have been identified and
eliminated, adjustments were undertaken in order to maintain consistency with
closely-related earlier studies.
