Addendum to "Variational Bounds in Positron-Atom Scattering"

Two additional positron-atom processes are treated using previously determined [Phys. Rev. 173, 190 1968] variational scattering functions: (1) Positronium formation in $e^{+}-\mathrm{H}$ collisions at threshold, and (2) the angular correlation between $e^{+}-\mathrm{He}$ annihilation quanta at zero energy. In case (1), we find a large reduction below the Born approximation, in qualitative agreement with other recent theoretical work. In case (2), very close agreement is found with the experiment of Briscoe et al.