Bragg reflection of low-energy positrons from the surface of graphite, Gullikson EM, Mills AP, Physical Review B, Volume 36, Number 16, pp. 8777-8779, 12/1/1987
Angle-Resolved Positronium Emission Spectroscopy, Chen DM, Berko S, Canter KF, Lynn KG, Mills AP, Roellig LO, Sferlazzo P, Weinert M, West RN, Physical Review Letters, Volume 58, Number 9, pp. 921-924, 3/2/1987