CCL: NDDO semiempirical parameters

Dear CCLers,,
 I have a couple of questions about semiempirical parameters in NDDO methods
 (MNDO, AM1...):
 1) Do you have any routine or the iterative formulas to obtain the derived
 parameters, rho1 and rho2, from the optimized ones (namely 1 center 2 electron
 integrals, g_ij, and zeta_i) ??
 2) Can you suggest any references which explicitly comment on the individual
 influence of the NDDO parameters upon calculated molecular properties?
   E.g.: If one varies the resonance integrals (beta_i), what is the effect upon
 geometries? Or if one varies the one center one electron integrals (U_ii), what
 is the effect upon charge distribution?
 Thank you very much for your help,
 Guilherme Menegon