( RelStr(# the carrier of (Sigma S), the InternalRel of (Sigma S) #) = RelStr(# the carrier of S, the InternalRel of S #) & RelStr(# the carrier of (Sigma T), the InternalRel of (Sigma T) #) = RelStr(# the carrier of T, the InternalRel of T #) ) by YELLOW_9:def 4;
hence Sigma f is continuous by WAYBEL17:29, WAYBEL21:6; :: thesis: verum