Electron-electron scattering: Spectral forms for the invariant amplitudes to ordere4

The five invariant amplitudes for electron-electron scattering to order $e^4$ are calculated using the causal methods of source theory. The basis set employed, which is free of kinematic singularities and zeros, consists of the Fermi invariants. The amplitudes are expressed in terms of double-spectral forms with accompanying single-spectral forms which are determined by analysis of causal forward scattering. The radiative corrections required for the analysis of polarization experiments are contained in these amplitudes.