src/HOL/Rings.thy
2010-02-10 haftmann 2010-02-10 dropped last occurence of the linlinordered accident
2010-02-10 haftmann 2010-02-10 moved less_eq, less to Orderings.thy; moved abs, sgn to Groups.thy
2010-02-10 haftmann 2010-02-10 division ring assumes divide_inverse
2010-02-08 haftmann 2010-02-08 renamed OrderedGroup to Groups; split theory Ring_and_Field into Rings Fields