Gordon Joly is wrong to state that the DSc, DLitt and so on are honorary degrees (Letters, January 15). Although they are often awarded honorarily, they can also be earned, typically by submitting a body of work that referees agree constitutes an internationally respectable contribution over a couple of decades.
The original questioner, Jan Smit (Letters, 1 January), could have obtained his answer much more efficiently by spending ten minutes looking up degrees on the Wikipedia website, which has articles on "Doctorate" and "PhD". These will answer his questions about such qualifications all over the world. If he prefers primary sources, most universities publish their degree regulations online.
Julian Bradfield, University of Edinburgh.