On the Crucial Significance of the Multi-Configuration Structure of a Bound State of Several Dirac Particles

The structure of a bound state of several Dirac particles is discussed. Relying on solid mathematical arguments of the Wigner-Racah algebra, it is proved the a non-negligible number of configurations is required for a description of this kind of systems. At present, the main results are not widely known and this is the underlying reason for the phenomenon called the proton spin crisis.