During the phase derivation in the case of non-centrosymmetric crystal structure, if one forces the phases to degenerate into a set of signs corresponding to those of the real parts of structure factors, it then results in an E-map containing simultaneously the actual structure and its enantiomorph. Such an E-map may in turn easily be retrieved by use of the component relation leading to a unique solution of the structure. With this procedure only two possible values (0 or π) are necessary to be considered for each unknown phase within the starting set. Hence the amount of calculation can be greatly reduced as compared with that of the ordinary phase permutation method.