theorem :: GROUP_24:54

for G1, G2 being Group
for N1 being normal Subgroup of G1
for N2 being normal Subgroup of G2
for phi being Homomorphism of G1,G2 st phi is bijective & phi .: the carrier of N1 = the carrier of N2 holds
G1 ./. N1,G2 ./. N2 are_isomorphic