In the original publication of this article, the equation on page 3, line 163 had an incorrect character.
The proper equation is as follows:
The publisher regrets this error.
Our systems are now restored following recent technical disruption, and we’re working hard to catch up on publishing. We apologise for the inconvenience caused. Find out more: https://www.cambridge.org/universitypress/about-us/news-and-blogs/cambridge-university-press-publishing-update-following-technical-disruption
Published online by Cambridge University Press: 15 February 2019
In the original publication of this article, the equation on page 3, line 163 had an incorrect character.
The proper equation is as follows:
The publisher regrets this error.