( 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