Halving operations apply for higher rank groups, like tetrahedral symmetry is a half group of octahedral group : h[4,3] = [1,4,3] = [3,3], removing half the mirrors at the 4-branch. The effect of a mirror removal is to duplicate all connecting nodes, which can be seen in the Coxeter diagrams: = , h[2p,3] = [1,2p,3] = [(p,3,3)].