BJORKEN, J. and S. L. Glashow , "Elementary particles and SU(4)", in Physics Letters 11 pp. 255–257, in the volume of 368pp, 1964. Bound in blue cloth. A lovely copy. $300

• Reprinted in  J. L. Rosner, New Particles. Selected Reprints, Stony Brook, Am. Ass. of Physics Teachers (1981) 15.
• “Proposal for the existence of a charmed fundamental fermion; First prediction of a Charmed Quark “ and

“Recently, models of strong interaction symmetry have been proposed involving four fundamental Fermion fields ψ>i and approximate symmetry under SU(4). Mesons are identified with bound states iψ>i and baryons with bound states i ψ>j ψ>k. In this note we examine a model of this kind whose principal achievements are these: a mass formula relating the masses of the nine vector mesons and predicting a ninth pseudoscalar meson at 950 MeV, a description of weak interactions including all selection rules except the nonleptonic Δ I = 1 / 2 rule, and a significant "baryon''-lepton symmetry. A new quantum number "charm'' is violated only by the weak interactions, and the model predicts the existence of many "charmed'' particles whose discovery is the crucial test of the idea. (Extracted from the introductory part of the paper.)--cited in “Chronology of Milestone Events in Particle Physics” (online).