Relativistic Coulomb Green's function in $d$-dimensions
  Using the operator method, the Green's functions of the Dirac and Klein-Gordon equations in the Coulomb potential $-Z\alpha/r$ are derived for the arbitrary space dimensionality $d$. Nonrelativistic and quasiclassical asymptotics of these Green's functions are considered in detail. 
R.N. Lee, A.I. Milstein, I.S. Terekhov
physics.atom-ph hep-ph