With the method of perturbative renormalization developed by Epstein and Glaser it is shown that Green's functions exist for theories with massless particles such as Q.E.D. and lambda:PHI/sup 2n/ theories. Growth properties are given in momentum space. In the case of Q.E.D., it is also shown that one can perform the physical mass renormalization.
Blanchard, P;  Seneor, R;  Ecole Polytechnique, 75 - Paris (France). Centre de Physique Theorique)
- European Organization for Nuclear Research, Geneva (Switzerland)