SHELX is a set of programs for the determination of small (SM) and macromolecular (MM) crystal structures by single crystal X-ray and neutron diffraction. In the program suite: SHELXT extracts the Laue group, cell dimensions and types of element present , solves the structure using data expanded to space group P1, and then uses the P1 phases to find the space group. SHELXS solves small (up to about 100 unique non-hydrogen atom) structures by direct methods. it is based on the classical tangent formula of Karle and Hauptman, but uses phase annealing and includes information from the weak reflections via the negative quartets. etc. etc,-> refer to the SHELX home page