The general position of the group P2/c (No. 13) The notation used here for subgroup chaining is an extension of the notation described at the BCS for its SUBGROUPGRAPH program , namely, G > Z1 > ... > Zn > H, where G would be the supergroup, and Z1-n and H would be subgroups. The transformation described in this case would be P2/m > P2/c, which, as we shall see, can be described in CLEG notation as P2/m > a-c,b,2c ; 0,0,1/2 > P2/c Essentially, CLEG notation combines the three aspects of space group reference, setting, and transform into one concise linear string for a "CLEG setting":