Driessen J.P.J., S.S.O. de Beek, H.C.W. Beijerinck, E.M. Spain, H.V. Parks, R. de Vivie-Riedle, and S.R. Leone, Comments On Atomic And Molecular Physics 32, 327-346 (1996).
Schuster J., A. Marte, S. Amtage, B. Sang, G. Rempe, and H.C.W. Beijerinck, Physical Review Letters 87, (2001).
Beijerinck H.C.W., E. Vredenbregt, R.J.W. Stas, M. Doery, and J. Tempelaars, Physical Review A 61, (2000).
and 
