1. J. A. Wheeler, “Polyelectrons”, Ann. New York Acad. Sci. 48, 219–238 (1946).
2. H. K. Avetissian, A. K. Avetissian, and G. F. Mkrtchian, “Self-Amplified Gamma-Ray Laser on Positronium Atoms from a Bose-Einstein Condensate”, Phys. Rev. Lett. 113, 023904 (2014).
3. K. F. Canter, P. G. Coleman, T. C. Griffith, and G. R. Heyland, “Measurement of total cross sections for low energy positron-helium collisions”, J. Phys. B: Atom. Molec. Phys. 5, L167 (1972).
4. D. G. Costello, D. E. Groce, D. F. Herring, and J. W. McGowan, “Evidence for the negative work function associated with positrons in gold”, Phys. Rev. B 5, 1433 (1972).
5. A. P. Mills, Jr., “Brightness Enhancement of Slow Positron Beams”, Appl. Phys. 23, 189 (1980).