1. M. Gell-Mann:A Schematic Model of Baryons and Mesons, submitted toPhys. Lett. We thank H. D. Taft for discussions on that paper.
2. R. K. Adair: private communication.
3. Y. Ne’eman:Nucl. Phys.,26, 222 (1961);M. Gell-Mann:Phys. Rev.,125, 1067 (1962), (an earlier version: CTSL-20 (1961) unpublished).
4. S. Meshkov, C. A. Levinson andH. J. Lipkin:Phys. Rev. Lett.,10, 361 (1963);S. L. Glashow andA. H. Rosenfeld:Phys. Rev. Lett.,10, 192 (1963).
5. The realization that distinctions equivalent to triality type may be made for SU3 representations is well known in the mathematical literature [H. Weyl,Lectures on Continuous Groups (Princeton, 1935);E. Stiefel: CommentariiMath. Helv.,14, 350 (1943); see also,M. Gourdin,Nuovo Cimento,30, 590 (1963) and references cited there.] What has not been emphasized hitherto is the importance of these distinctions for combining representations (interactions). Let us note, too, that-in order to be brief-we are not distinguishing between the ideas « operators on a representation », and « the combining of representations ». We have thus assumed implicitly the concept of tensor operators; that is, the mapping: operators → states, which is (except for SU2 ) a many-to-one mapping. The solution to the resulting multiplicity problem has been presented inL. C. Biedenharn:Phys. Lett.,3, 254 (1963); but is inessential to the present work and need not concern us further.