STABLE EXTENSIVE GAME FORMS.

Peleg established a fundamental theorem which says that convex effectivity functions are stable. He also proved its partial converse: Within the class of maximal effectivity functions, stability implies convexity. The present paper provides another partial converse: Within the class of α-effectivity functions derived from extensive game forms (without chance moves), stability implies convexity. It also provides a geometric characterization of the stability condition for the latter class. [ABSTRACT FROM AUTHOR]