Reading volume 1 of Weinberg's QFT book, chapter 12, page 505 he says that if you consider a diagram with degree of divergence D≥0, its contribution can written as a polynomial of order D in external momenta. As an example he considers the D=1 integral
∫∞0kdkk+q=a+bq+qlnq
where a and b are divergent constants, and we see that we get a polynomial or order 1 in the external momenta q. He then says, and I quote
"Now, a polynomial term in external momenta is just what would be produced by adding suitable terms to the Lagrangian, if a graph with Ef external lines of type f (refering to field type) has degree of divergence D≥0, then the ultraviolet divergent polynomial is the same as would be producedby adding various interactions i with nif=Ef fields of type f and di≤D derivatives."
can anybody elaborate on this a bit? in particular, how and where does the polynomial arise with the added Lagrangian term?