"That electron-phonon interactions lead to an effective attractive interaction between electrons by exchange of virtual photons was shown by Fröhlich by use of field-theoretic methods. His analysis was extended by Pines and myself to include Coulomb interactions. In second order, there is an effective interaction between the quasi-particle excitations of the normal state which is the sum of the attractive phonon-induced interaction and a screened Coulomb interaction. In the Handbuch article, I suggested that one should take the complete interaction, not just the self-energy tens, and use it for a theory of superconductivity."