Diffraction symbols. Erratum

In the paper published under the above title (Donnay & Kennard, 1964), please restore omitted words as follows: Page 1340, column 1, line 3 up: after the word aspect, insert P3_{1, 2}** into. Note also that the space-group symbols used in this paper are those of the 1935 edition of the International Tables. Any screw axis that results from intersecting symmetry planes need not be explicitly symbolized, although this was done in the 1952 edition. Examples: P4mc = P4₂mc, I4md = I4₁md, Pbc2 = Pbc2₁. The subscripts can easily be added by those who prefer the more explicit symbolism. We feel an explanation is in order, in view of the correspondence we received on this particular point.