The approach to defining common knowledge outlined above can be viewed as a recipe for defining common (robust/strong) belief (simply replace the knowledge operators \(K_i\) with the appropriate belief operator). See Bonanno (1996) and Lismont &amp; Mongin (1994, 2003) for more information about the logic of common belief. Although we do not discuss it in this entry, a probabilistic variant of common belief was introduced by Monderer &amp; Samet (1989).