1 D.H. Crandall, R.A. Phaneuf, B.E. Hasselquist, and D.. Gregory, Journal of Physics B: Atomic and Molecular Physics 12, (1979).
1 P.. Taylor, D.. Gregory, G.H. Dunn, R.A. Phaneuf, and D.H. Crandall, Physical Review Letters 39, (1977).
1 D.H. Crandall, W.E. Kauppila, R.A. Phaneuf, P.. Taylor, and G.H. Dunn, Physical Review A 9, (1974).