The publisher apologises that upon publication of the article, the second derivative on the right-hand side of equation 3.21 was mistyped and thus presented incorrectly as
![](https://static.cambridge.org/binary/version/id/urn:cambridge.org:id:binary:20221027084145807-0450:S002211202200859X:S002211202200859X_eqn1.png?pub-status=live)
The correct equation should be as below
![](https://static.cambridge.org/binary/version/id/urn:cambridge.org:id:binary:20221027084145807-0450:S002211202200859X:S002211202200859X_eqn2.png?pub-status=live)
Published online by Cambridge University Press: 27 October 2022
The publisher apologises that upon publication of the article, the second derivative on the right-hand side of equation 3.21 was mistyped and thus presented incorrectly as
The correct equation should be as below