Lorentz Covariant Spin-Grouping of Baryon Resonances
  A well pronounced spin--grouping of baryon resonances to O(4) partial waves is found in baryon spectra and shown to be well interpreted in terms of Lorentz group representations of the type (1/2 +l', 1/2 +l')* [(1/2, 0)+(0,1/2)] with l' integer. In this way the relativistic description of finite dimensional resonance towers containing higher-spin states becomes possible. It is further argued that the nucleon excitations into the l'=1 and l'=2 multiplets are chiral phase transitions. 
M. Kirchbach