doi:http://dx.doi.org/10.1017/psrm.2013.1, Published by Cambridge University Press 2013.
The authors would like to correct a mistake in the expression below.
The mistake is in expression 1. This reads
![](https://static.cambridge.org/binary/version/id/urn:cambridge.org:id:binary:20160312001223645-0054:S2049847013000265_eqnU1.gif?pub-status=live)
Whereas it should have read
![](https://static.cambridge.org/binary/version/id/urn:cambridge.org:id:binary:20160312001223645-0054:S2049847013000265_eqnU2.gif?pub-status=live)
12th August 2024: digital purchasing is currently unavailable on Cambridge Core. Due to recent technical disruption affecting our publishing operation, we are experiencing some delays to publication. We are working hard to restore services as soon as possible and apologise for the inconvenience. For further updates please visit our website: https://www.cambridge.org/news-and-insights/technical-incident
Published online by Cambridge University Press: 08 November 2013
doi:http://dx.doi.org/10.1017/psrm.2013.1, Published by Cambridge University Press 2013.
The authors would like to correct a mistake in the expression below.
The mistake is in expression 1. This reads
Whereas it should have read