“…It can be found that the elements in the class [2] and the class [22] are all the elements of order 2. However, the elements in the class [2] represent the rotation around the 2fold axes connecting the midpoints of two opposite edges, while the elements in the class [22] represent the rotations around the three coordinate axes through the angle π respectively. The permutation subgroup which is isomorphic to the group O is {E, (123), (132), (234), (243), (124), (142), (134), (143), (12) (34), (13) (24), (14) (23), (12), (13), (14) To summarize, on the basis of theoretical calculation and analysis, there are 11300 subgroups of the permutation group S 7 .…”