在 Sobolev (1975) Reduction 的作用下，我們證明當一對局是凸集，它的reduced game 也會呈現凸集。此外，我們將分別在essential及superadditive的對局集合中找到二個最大的子集，使得它的reduced game，也會滿足essential及superadditive的對局特徵。 Under reduction in the sense of Sobolev [4], we will show that a game is convex, so are its reduced games. Besides, we will find 2 maximal subclasses with respect to essential and superadditive criteria such that a game is in one subclass, so are its redu
