Simple negatively ordered implicative semigroups(continued)
Zeng Qing-yi · Journal of Shaoguan University · 2012
A negatively ordered implicative semigroup(S,≤,·)is called simple if all ordered filters of S are {1} and S itself.Let(S,≤,·) be a commutative negatively ordered implicative semigroup,then(S,≤,·)is simple if and only if all *-congruences of S are IS and S×S.