Nobel prize to M. Gell-Mann awarded in 1969 "for his contributions and discoveries concerning the classification of elementary particles and their reactions''
Gell-Mann, M.; A Schematic Model of Baryons and Mesons
Phys. Lett. 8 (1964) 214;
M. Gell-Mann and Y. Ne'eman, The Eightfold Way: A Review - With Collection of Reprints, Frontiers in Physics, ed. D. Pines, W. A. Benjamin, Inc. New York - Amsterdam (1964) 168.
It is suggested that an SU(3) scheme ought to have unitary triplets as its fundamental objects. The simplest possibility consists of the triplet with spin 1/2, baryon number 1/3, and containing an isotopic doublet with charges 2/3 and -1/3, and a singlet with charge -1/3. The consequences of assuming that interaction Lagrangians are made up of such objects ("Quarks'') are discussed. One of the quarks should be stable, so a search is suggested. (Science Abstracts. 1964, 15007. E. J. Squires.).
Related references See also Y. Ne'eman, Nucl. Phys. 26 (1961) 222;
M. Gell-Mann, Phys. Rev. 125 (1962) 1067;
R. H. Capps, Phys. Rev. Lett. 10 (1963) 312;
R. E. Cutkosky, J. Kalckar, and P. Tarjanne, Phys. Lett. 1 (1962) 93;
E. Abers, F. Zachariazen, and A. C. Zemach, Phys. Rev. 132 (1963) 1831;
N. Cabibbo, Phys. Rev. Lett. 10 (1963) 531;
R. E. Cutkosky and P. Tarjanne, Phys. Rev. 132 (1963) 1354;
P. Tarjanne and V. L. Teplitz, Phys. Rev. Lett. 11 (1963) 447;
J. Joyce, Finnegan's Wake Viking Press, New York (1939) 383;
M. Gell-Mann and M. Levi, Nuovo Cim. 16 (1960) 705;
S. L. Glashow, Phys. Rev. 130 (1963) 2132;
Introduction of quarks as fundamental building blocks for hadrons.