1. M. Ademollo, H. R. Rubinstein, G. Veneziano andM. A. Virasoro:Phys. Rev. Lett.,19, 1402 (1967);Phys. Lett.,27 B, 99 (1968);G. Veneziano:Nuovo Cimento,57, 190 (1968);M. A. Virasoro:Phys. Rev. Lett.,22, 37 (1969);K. Bardakci andH. Ruegg:Phys. Lett.,28 B, 342 (1968);H. M. Chan:Phys. Lett.,28 B, 425 (1969);C. Goebel andB. Sakita:Phys. Rev. Lett.,22, 257 (1969).
2. K. Kikkawa, B. Sakita andM. A. Virasoro:Feynman-like diagrams compatible with duality, University of Wisconsin preprint COO-224 (1969);
3. K. Bardakci, M. Halpern andJ. Shapiro: University of California preprint;G. Frye andL. Susskind:Feynman diagrams and duality, Yeshiva University preprint.
4. This model was first put forward by the author inL. Susskind:Physical interpretation of duality, Yeshiva University preprint. The formal manipulations in the model were independently discovered slightly earlier byY. Nambu: University of Chicago preprint;S. Fubini, P. Gordon andG. Veneziano:Phys. Lett., and the author, Yeshiva University preprint,Structures of hadrons implied by duality.
5. H. Harari:Phys. Rev. Lett.,22, 689 (1969);J. L. Rosner:Phys. Rev. Lett.,22, 689 (1969).