theorem Th8: :: MFOLD_2:8

for T1, T2, T3 being TopSpace
for A1 being Subset of T1
for A2 being Subset of T2
for A3 being Subset of T3 st A1,A2 are_homeomorphic & A2,A3 are_homeomorphic holds
A1,A3 are_homeomorphic