This result also makes sense regarding space group P2₁/c which has four asymmetric units in the cell. This molecule lacks a center of symmetry so it cannot lie on a special position; the asymmetric unit must equal one molecule. The strategy to be employed in solving this structure will be to locate the Br atom (the heavy atom) from a Patterson map and then calculate a Fourier electron density map phased on the Br atom in order to locate the other atoms in the molecule.
In order to interpret a Patterson map in P2₁/c, an analysis of the expected heavy atom vectors is necessary. This can be accomplished by filling in a vector grid in a scheme like:

By completing this grid, x, y, z expressions for all the heavy atom vectors will be obtained. On the next page, this grid has been completed.