theorem :: GROUP_11:79

for G being Group
for N, N1, N2 being normal Subgroup of G st N1 is Subgroup of N2 holds
ex N3, N4 being strict normal Subgroup of G st
( the carrier of N3 = N ~ N1 & the carrier of N4 = N ~ N2 & N3 ~ N1 c= N4 ~ N1 )