1 O.. Poulsen, N.. Bjerre, E.. Riis, S.A. Lee, and J.L. Hall, in (World Scientific Pub Co Inc, 1989), p. 589\textendash612.
1 J.E. Faller, P.L. Bender, J.L. Hall, D.. Hils, R.T. Stebbins, and M.A. Vincent, Advances in Space Research 9, (1989).
1 E.. Riis, L.-U.. Andersen, N.. Bjerre, O.. Poulsen, S.. Lee, and J.L. Hall, Physical Review Letters 60, (1988).