1. Interacting-string picture of dual-resonance models
2. M. Kaku and K. Kikkawa, City College of CUNY preprints I and II (1974), to be published in Phys. Rev. D.
3. J. Scherk, New York University preprint NYU/TR3/74, to be published in Reviews of Modern Physics.
4. P. Ramond, Yale University preprint (1974)