computation of convolution products



 Dear netters,
 Dealing with momentum space Hartree-Fock equations, I have to compute
 integrals I(p) including convolution products:
   I(p)=INT(dq W(q) F(q-p) )
      where W(q)=INT(dp G(p) H(p-q) )
 INT stands for three dimensional integrations and F,G,H are three dimensional
 functions.
 Such a computation is not trivial for me and I meet difficulties. Can you help
 me? Any references of papers or programs are welcome.
                                              Thank you for your help.
 PS: my own e-mail adress is DEWINDT at FRSAC11.BITNET