theorem Th121: :: GLIBPRE1:118

for S1, S2 being GraphUnionSet
for G1 being GraphUnion of S1
for G2 being GraphUnion of S2 st ( for H2 being Element of S2 ex H1 being Element of S1 st H2 is Subgraph of H1 ) holds
G2 is Subgraph of G1