There are two kinds of superspace-group symbols [see Section 3.1 and Table 1 of A. Yamamoto's
paper, *Acta Cryst.* (1996) A**52** 509-560], i.e. one-line symbols and two-line
symbols. For historical reason, the program *SPGR4D* [*J. Appl. Cryst.* (1997).
**30**, 73-78] in *DIMS* can only recognize two-line symbols. The program
*symbol1to2* is wriitten for converting one-line symbols to two-line symbols of
(3+1)-dimensional superspace groups. It can distinguish two-line symbols from one-line
symbols. When the input symbol belongs to two-line symbols, *symbol1to2* will invoke
*SPGR4D* and pass on directly the input
symbol to it. *SPGR4D* will then derive and output the corresponding symmetry operations.
On the other hand, if the input symbol belongs to one-line symbols, *symbol1to2* will derive
the corresponding two-line symbol and then pass on the result to *SPGR4D* to get the
symmetry operations.

775 non-equivalent one-line symbols of (3+1)-dimensional superspace groups listed in the
International Tables for Crystallography [Janssen, T., Janner, A., Loouenga-Vos, A., de Wolff,
P.M. (2006) *International Tables for Crystallography* Vol. C, Chapter 9.8, Table 9.8.3.5,
pp. 922-934] were input to *symbol1to2* and the resultant symmetry operations from
*SPGR4D* were compared with those listed by Ivan P. Orlov on the Web at
*http://superspace.epfl.ch/groups/*. There are 229 among the total 775 superspace groups,
of which symmetry operations derived by *SPGR4D* are different from that listed by Orlov.
This is owing to the shift of unit-cell origin and/or the direction choice of the 4th axis.
Details are available **here**.

**Reference**

Li, X.M., Li, F.H. & Fan, H.F. (2009). A revised version of the program VEC. *Chinese Physics
B* **18**, 2459-2463.