How to read (and understand) Volume A of International Tables for Crystallography: an introduction for nonspecialists

Dauter, Z.; Jaskolski, M.

doi:10.1107/S0021889810026956

Figure 5
Point-group symmetry: (a) 3m of chloromethane (CH₃Cl) and (b) mm2 of dichloromethane (CH₂Cl₂).