2014-01-16 blanchet 2014-01-16 moved 'Zorn' into 'Main', since it's a BNF dependency
2013-05-24 popescua 2013-05-24 fixed files broken due to Zorn changes (cf. 59e5dd7b8f9a)
2011-09-11 wenzelm 2011-09-11 misc tuning and clarification;
2009-10-17 wenzelm 2009-10-17 eliminated hard tabulators, guessing at each author's individual tab-width; tuned headers;
2009-06-24 wenzelm 2009-06-24 standard naming conventions for session and theories;