The zonal reflection conditions are the general reflection conditions due to the presence of glide planes. The resulting conditions apply only to two dimensional sets of reflections, i.e. to reciprocal-lattice nets containing the origin (such as hk 0, h 0 l , 0 kl , hhl ). For instance, for a glide plane parallel to (001): type of reflection reflection condition glide vector glide plane 0kl k = 2 n b/2 b 0kl l = 2 n c/2 c 0kl k + l = 2 n b/2 + c/2 n 0kl k + l = 4 n k, l = 2n b/4 ± c/4 d The zonal reflection conditions are listed in Table 2.2.13.2 of International Tables of Crystallography, Volume A .