Blue in Sherpa: Author's Pre-print: author cannot archive pre-print (ie pre-refereeing) Author's Post-print: author cannot archive post-print (ie final draft post-refereeing) Publisher's Version/PDF:   author can archive publisher's version/PDF LL 26.5.14, Requested (Brian) Permission, 22.8.14-MMM. Received 26.8.14-MMM. Supporting documentation added to dark upload - HD 15/11/17