) ▁- ▁Ch ang ▁ ▁References ▁ ▁https :// www . im db . com / name / nm 1 1 7 3 7 3 4 / ▁http :// www . mov iet ome . com / people / 2 5 1 3 4 3 / th omas - ho / index . html ▁ ▁External ▁links ▁ ▁Category : 1 9 7 3 ▁birth s ▁Category : L iving ▁people ▁Category : English ▁male ▁film ▁actors ▁Category : English ▁male ▁stage ▁actors ▁Category : English ▁male ▁television ▁actors ▁Category : English ▁male ▁voice ▁actors ▁Category : H ong ▁Kong ▁em igr ants ▁to ▁England ▁Category : Pe ople ▁from ▁K ow lo on <0x0A> </s> ▁A ▁zone ▁diagram ▁is ▁a ▁certain ▁geometric ▁object ▁which ▁a ▁variation ▁on ▁the ▁notion ▁of ▁Vor ono i ▁diagram . ▁It ▁was ▁introduced ▁by ▁T ets uo ▁As ano , ▁J iri ▁Mat ouse k , ▁and ▁T akes hi ▁Tok uy ama ▁in ▁ 2 0 0 7 . ▁ ▁Form ally , ▁it ▁is ▁a ▁fixed ▁point ▁of ▁a ▁certain ▁function . ▁Its ▁existence ▁or ▁uniqu eness ▁are ▁not ▁clear ▁in ▁advance ▁and ▁have ▁been ▁established ▁only ▁in ▁specific ▁cases . ▁Its ▁computation ▁is ▁not ▁obvious ▁too . ▁ ▁A ▁particular ▁but ▁inform ative ▁case ▁Consider ▁a ▁group ▁of ▁ ▁different ▁points ▁ ▁in ▁the ▁E uclidean ▁plane . ▁Each ▁point ▁is ▁called ▁a ▁site . ▁When ▁we ▁speak ▁about ▁the ▁Vor ono i ▁diagram ▁induced ▁by ▁these ▁sites , ▁we ▁associate ▁to ▁the ▁site