2010-03-01 haftmann 2010-03-01 replaced a couple of constsdefs by definitions (also some old primrecs by modern ones)
2010-02-08 haftmann 2010-02-08 renamed OrderedGroup to Groups; split theory Ring_and_Field into Rings Fields
2010-02-05 haftmann 2010-02-05 more consistent naming of type classes involving orderings (and lattices) -- c.f. NEWS
2009-10-20 wenzelm 2009-10-20 modernized session Metis_Examples;