van Kempen E.G.M., S. Kokkelmans, D.J. Heinzen, and B.J. Verhaar, Physical Review Letters 88, (2002).
Gibble K.E., C. Fertig, R. Legere, J.I. Rees, S. Kokkelmans, and B.J. Verhaar, in (World Scientific, 2002).