c1 Refereed Journal Article. Green in Sherpa; Author's Pre-print: author can archive pre-print (ie pre-refereeing)  Author's Post-print: author can archive post-print (ie final draft post-refereeing)  Publisher's Version/PDF: author cannot archive publisher's version/PDF  --MA 21/2/14. Requested (Patrick) Accepted v. & Permission, 31.7.14-MMM. Patrick supplied publisher version, 7.8.14-MMM.
Sherpa Checked again, added file from Symplectic dup, 24.3.16--MMM