The study of spherical-deformed ground--state phase transitions in finite
nuclei as a function of N and Z is hindered by the discrete values of the
nucleon number. A resolution of the integer nucleon number problem, and
evidence relating to phase transitions in finite nuclei, are discussed from the
experimental point of view and interpreted within the framework of the
interacting boson model.Comment: 8 pages Latex + 8 figs (postscript). In Phys Rev Lett, June 199