r:Rng, a, b, c:|r|. (a +r (b +r c)) = ((a +r b) +r c)  |r| 

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Up	rings 1
Definitions of Statement	Rng, r+gp
Definitions	t  T, IMonoid, x f y, x:A. B(x), t.2, t.1, , P & Q, Mon, Group{i}, r+gp, *, |g|
Lemmas	rng wf, grp wf, grp id wf, grp op wf, grp car wf, monoid p wf, add grp of rng wf a, mon assoc