1. A short review of previous results: an extended perturbative
   scheme for a localizable effective theory of strong interaction;
   reduction procedure and minimal parameters; minimal set of
   renormalization prescription fixing physical contents of an
   effective theory.
2. The method of Cauchy forms for functions of two variables
3. A test ground for our methods: Lovelace string amplitude (short
   review of general properties); Cauchy forms for the string
   amplitude.
4. The notion of duality revisited; bootstrap constraints for the
   string-like amplitude.
5. Numerical tests of sum rules that follow from the bootstrap system
   for string-like amplitude.
6. Renormalization prescriptions fixing tree-level 4-leg vertices in
   a realistic effective scattering theory.