This paper introduces a few characterizations of quasi continuity of functions and minimality of multifunctions. The methods used are based on the concept of cluster systems and derived operations acting on multifunctions. Inclusion relations between original multifunction and resultant cluster multifunction describe properties connected with generalized continuities and minimality.
"Minimality of Multifunctions." Real Anal. Exchange 32 (2) 519 - 526, 2006/2007.