1. Y. Nambu and G. Jona-Lasinio, Phys. Rev., 122, 345 (1961).
2. T. Eguchi and H. Sugawara, Phys. Rev., D10, 4257 (1974); K. Kikkawa, Prog. Theor. Phys., 56, 947 (1976); H. Kleinert, Understanding the Fundamental Constituents of Matter, A. Zichichi, ed., Plenum Press, New York (1978); D. Ebert and M. K. Volkov, Z. Phys., C16, 305 (1983).
3. S. P. Klevansky, Rev. Mod. Phys., 64, 649 (1992).
4. T. Hatsuda and T. Kunihiro, Phys. Rep., 247, 221 (1994).
5. E. N. Nikolov et al., Nucl. Phys., A608, 411 (1996).