1.Department of Basic Courses, Zhejiang Shuren University, Hangzhou 310015 2.College of Information Science and Engineering, Zhejiang Normal University, Jinhua 321004
Abstract：Let φ be a surjective homomorphic mapping from group G to group K. Through the congruence relation ρ from K to G by φ, the property, that the surjective homomorphic mapping φ can commutate with the upper (lower) approximation of the congruence relation, is obtained. It is shown that a homomorphic mapping keeps upper (lower) rough subgroups, and upper (lower) rough left (right, twosided) ideally unchanged.
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2006, Vol. 19 
