Mc Gettrick, Michael http://orcid.org/0000-0003-3400-6569
Article History
Accepted: 26 December 2019
First Online: 30 January 2020
Change Date: 13 July 2020
Change Type: Correction
Change Details: The equation at the beginning of Sect.��4.4, and also Eq.��(45) at the end of Appendix B, should both be replaced by IF��=��23/72.