The main result of this paper dates back to my PhD. thesis (1991), but the full paper only became available in 1999 as a technical report of the Eindhoven Univerisity of Technology (The Netherlands). The paper has been published in the Journal of Recreational Mathematics, 31(2): 117-126, 2002/2003.
A preprint is available in the following formats: compressed postscript, HTML, PDF.