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computer programs
The program TWINLAW reads two orientation matrices obtained from a non-merohedrally twinned crystal and evaluates the twin law. In a second step, the program HKLF5 uses this twin law to generate a reflection file for refinement with the HKLF5 option of the SHELXL program. The use of both programs is demonstrated by means of the structure determination of Sr(H2PO4)2·H2O.