1. http://positron.physik.uni-halle.de/EPOS/
2. Production of Highly Polarized Positrons Using Polarized Electrons at MeV Energies
3. Allen Mills noted “The spin polarized gas has to be spin aligned atomic H so the annihilation rate differs by a factor of 372 between positrons polarized parallel and antiparallel to the H spins”, in a conversation with the authors.
4. The Jefferson Lab Free Electron Laser Program
5. See Positron Beams and Their Applications, edited by P. G. Coleman (World Scientific, Singapore, 2000).