src/HOL/Library/Preorder.thy
2016-07-12 wenzelm 2016-07-12 misc tuning and modernization;
2015-10-10 wenzelm 2015-10-10 prefer symbols;
2015-10-09 wenzelm 2015-10-09 discontinued specific HTML syntax;
2015-06-17 wenzelm 2015-06-17 isabelle update_cartouches;
2014-11-02 wenzelm 2014-11-02 modernized header;
2009-05-07 haftmann 2009-05-07 better to have distinguished class for preorders
2009-05-07 haftmann 2009-05-07 added theory for explicit equivalence relation in preorders