1. Coleman, S.: The uses of instantons. In: Proceedings of the International School of Physics, Erice, Italy, 1977 (to appear)
2. Harrell, E.M.: Commun. Math. Phys.60, 73?95 (1978)
3. Br�zin, E., Parisi, G., Zinn-Justin, J.: Phys. Rev. D16, 408?412 (1977)
4. Isaacson, D.: Comm. Pure App. Math.29, 531?551 (1976)
5. Fr�man, N., Fr�man, P.-O.: JWKB approximation, contribution to the theory. Amsterdam: North-Holland, 1965;