1. For a review of the problems of present LGT calculations seeG. Preparata:The magnetic instability of the perturbative Yang-Mills vacuum, inVariational Calculations in Quantum Field Theory, edited byL. Polley andD. E. L. Pottinger (World Scientific, Singapore, 1988).
2. E. Eichten et al.:Phys. Rev. Lett.,34, 369 (1975).
3. J. L. Richardson:Phys. Lett. B,82, 272 (1979);D. D. Stanley andD. Robson:Phys. Rev. Lett.,45, 235 (1980);F. Schöberl:Z. Phys. C,15, 261 (1982);S. Godfrey andN. Isgur:Phys. Rev. D,32, 189 (1985);R. McClary andN. Byers:Phys. Rev. D,28, 1692 (1983).
4. For a pedagogical description of those developments seeG. Preparata:The standard model: its foundations and its problems, inHadronic Physics at Intermediate Energies, edited byT. Bressani andR. Ricci (Elseviers Science Publ. B. V., 1986).
5. G. Preparata:Nuovo Cimento A,103, 1073 (1990).