The Bilbao Crystallographic Server (BCS), at web address https://cryst.ehu.es/, provides a nearly comprehensive guide and utility collection for symmetry, including space group tables, analysis tools and specialized computational capabilities for areas such as spectroscopy. By my estimate, there are close to 200 utilities available at this site, so no short description can do justice to this absolutely wonderful resource in crystallography. The site provides tutorials and you can download extensive slide decks from prior week-long training workshops about the BCS from the site.
As just one example of just one hidden gem, I can recall a now long-retired mentor showing me a folder containing many photocopied (back then we would have said xeroxed) pages of subgroup-supergroup relationships as graphs that showed their interconnections. He explained that this material had never been published, but he knew someone who knew someone who had prepared the material. At the time, I did not appreciate the value of being able to see these relationships as a graphic or I might have asked to make a copy of his copy myself. Now, you can generate these graphs as needed with BCS program SUBGROUPGRAPH (in the Group-Subgroup Relations grouping). Enter the parent and child space group numbers and the intervening subgroups are listed. Ask for a graph and that is then shown. An example is given in Fig. 28.1, where the figure is taken directly from the web page.
