src/HOL/Library/Preorder.thy
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