Let N be a normal subgroup of a group G. The factor group or
For each aN and bN in G/N, the
- (aN)(bN) = a(Nb)N = a(bN)N = (ab)NN = (ab)N.
The inverse of an element aN of G/N is a-1N.
The factor group G/T of a space group G and its translation
Chapter 8 in the International Tables of Crystallography, Volume A