International Tables for Crystallography is the definitive resource and reference work for crystallography and structural science.

Volume A1, an extension of and supplement to Volume A, presents a systematic treatment of the maximal subgroups and minimal supergroups of the crystallographic plane groups and space groups. The volume is divided into 3 parts:

Part 1: An introduction to the theory of space groups at various levels and with many examples.
Part 2: A complete listing of all maximal subgroups and minimal supergroups for each plane...