When this keyword is present, * GraphEnt* expects to read 7 (and only 7) columns for each
reflection record, which will be interpreted as
*h*, *k*, *l*,| *F*_{1}|,(| *F*_{1}|),| *F*_{2}|,(| *F*_{2}|) for a difference Patterson calculation.
The difference and its standard deviation will be calculated, the resulting data
will be squared and the phases set to zero before the calculation is started.

NMG, Nov 2002