theorem :: GRAPH_1:6

for G1, G2 being Graph st the Source of G1 tolerates the Source of G2 & the Target of G1 tolerates the Target of G2 holds
( the Source of (G1 \/ G2) = the Source of G1 \/ the Source of G2 & the Target of (G1 \/ G2) = the Target of G1 \/ the Target of G2 )