We thank K. Tsiganis for many clarifying discussions, M. Georgoulis for letting us profit from his experience in constructing cellular automata models, and the referee R.J. Hamilton for his comments and advice. The work of H. Isliker was supported by a grant of the Swiss National Science Foundation (NF grant nr. 8220-046504). The work of A. Anastasiadis, D. Vassiliadis, and L. Vlahos was supported by a PENED program of the Greek General Secretariat of Research and Technology.
© European Southern Observatory (ESO) 1998
Online publication: June 26, 1998