2009-07-27 ago "more standard" argument order of relation composition (op O)
2009-03-02 ago name changes
2008-07-25 ago added class preorder
2007-07-11 ago Adapted to new inductive definition package.
2005-06-17 ago migrated theory headers to new format
2005-02-01 ago the new subst tactic, by Lucas Dixon
2003-01-31 ago conversion to new-style theories and tidying
2001-12-01 ago renamed class "term" to "type" (actually "HOL.type");
1999-06-10 ago using the new GenPrefix theory
1999-05-24 ago lists are partially ordered by the prefix relation