1. Geonium theory: Physics of a single electron or ion in a Penning trap
2. G. Gabrielse, W. Jhe, D. Phillips, Harvard University, Cambridge, MA 02138, USA.
3. H. Kalinowsky, Mainz University, Institute of Physics, Germany.
4. P. DeCecco, P. Hauser, F. Kottmann, L.M. Simons, Paul Scherrer Institute, CH 5231 Villigen, Switzerland.
5. D. Horvarth, Central Research Institute for Physics, H-1525 Budapest, Hungary.