Existence theorems of equilibrium points in stackelberg

Abstract
A two players static. Stackelberg game is considered with constraints on the decision variables. Existence theorems of equilibrium points are given when the reaction set of the follower to the strategy of the leader, is a singleton. Some definition are presented and discussed and a simple existence theorem is given also in the case when the follower has more than one element in his reaction set. Finally an example of dynamic Stackelbebg game- is analized to emphasize some features arising when constraints are present on control variables.