2014-11-02 wenzelm 2014-11-02 modernized header;
2014-06-11 Thomas Sewell 2014-06-11 Hypsubst preserves equality hypotheses Fixes included for various theories affected by this change.
2012-03-15 paulson 2012-03-15 replacing ":" by "\<in>"
2012-03-08 paulson 2012-03-08 Structured and calculation-based proofs (with new trans rules!)
2012-03-06 paulson 2012-03-06 Using mathematical notation for <-> and cardinal arithmetic
2012-03-06 paulson 2012-03-06 mathematical symbols instead of ASCII
2011-11-20 wenzelm 2011-11-20 eliminated obsolete "standard";
2011-02-18 wenzelm 2011-02-18 more precise headers;
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).