Revision 57

Rewordings and some restruturing of the document, to attempt to address
  concerns on the list (clearer now?).
Document run through a spellchecker: fix typos and make the spelling
  consistently cisatlantic (it was Azorean before)
Fix some references, and how they're formatted by BibTeX
  (cite by editors, where available, in preference to authors)
Tweak xrefs format.