Fine-Structure Measurement in the First Excited State of Positronium*, Mills AP, Berko S, CAnter KF, Physical Review Letters, Volume 34, Number 25, pp. 1541-1544, 6/23/1975
Effects of collisions on the magnetic quenching positronium, Mills AP, The Journal of Chemical Physics, Volume 62, Number 7, pp. 2646-2659, 4/1/1975