Nonperturbative Green's function approach to quantum field theory and arbitrariness of solutions

Green's function equations are considered for interacting spinor and (pseudo) scalar fields with interactions gbarpsiγpsiphi + 1/4 lambdaphi4. These equations do not determine higher many-point functions if two-point functions are given as 'input'. If vertex parts are given as input, two-point functions are determined but higher many-point functions are not determined. (author)