Semivalues of Simple Games

It is shown that each semivalue (bounded semivalue) on the class SG of monotonic simple games with a finite support can be uniquely extended to a semivalue (continuous semivalue) on the class G of all games with a finite support. We use this to show that the formula that is given for semivalues (continuous semivalues) on G by Dubey, Neyman and Weber also holds for semivalues (bounded semivalues) on SG. We also derive another formula for semivalues on SG (in terms of the minimal winning coalitions of the game).