  This paper is a companion article to the review paper by the present author
devoted to the classification of matter constituents (chemical elements and
particles) and published in the first part of the proceedings of The Second
Harry Wiener International Memorial Conference (see quant-ph/0310155). It is
mainly concerned with a group-theoretical approach to the Periodic Table of the
neutral elements based on the noncompact group SO(4,2)xSU(2).
