Most of quotations marks are palindroms: "..." 66---99, `` ...'', ``...,,
<< ... >>, pp ... qq etc.
Fernand Baudin, a Belgium specialized in intellgient typography, and author of
a very good book "l'Effet Gutenberg", wrote, years ago,
a small pamphlet on these quotations marks and their correspondances
in some European countries. It has been reprinted in Cahiers GUTenberg number7
(1991) and should be available soon, in French, on the Web.