2012-03-06 paulson 2012-03-06 mathematical symbols instead of ASCII
2011-11-20 wenzelm 2011-11-20 eliminated obsolete "standard";
2010-03-02 wenzelm 2010-03-02 standard convention for syntax consts;
2010-02-11 wenzelm 2010-02-11 numeral syntax: clarify parse trees vs. actual terms; modernized translations; formal markup of @{syntax_const} and @{const_syntax};
2010-02-10 wenzelm 2010-02-10 modernized translations;
2009-10-17 wenzelm 2009-10-17 eliminated hard tabulators, guessing at each author's individual tab-width; tuned headers;
2008-02-11 krauss 2008-02-11 Made theory names in ZF disjoint from HOL theory names to allow loading both developments in a single session (but not merge them).