Positron mobility in perylene, Mills AP, Karl N, Physical Review B, Volume 48, Number 10, pp. 7050-7056 , 9/1/1993
Measurement of the Positronium 13S1-23S1 Interval by Continuous-Wave Two-Photon Excitation, Fee MA, Mills AP, Chu S, Shaw ED, Danzman K, Chichester RJ, Zuckerman DM, Physical Review Letters, Volume 70, Number 10, pp. 1397-1400, 3/8/1993