Bodie Douglas is Professor Emeritus of Chemistry of the University of Pittsburgh. He has had three editions of an inorganic chemistry textbook and a textbook on symmetry and group theory. He spent a year with the crystallographic group of Sir Gordon Cox at the University of Leeds (England). Shi-Ming Ho retired from Westinghouse Research Laboratory where he worked in materials science. Ideas for the system used for describing structures in this book were part of his doctoral dissertation with Bodie Douglas.