4039 C. Bruni/G. Koch: Modelling the cell cycle with quiescent compartments. Math. Models Meth. Appl. Sci. 2/1 (1992), 53-78. 2049 D. Lichtstein/H. Atlan: The cellular state - the way to regain specificity and diversity in hormone action. J. Theor. Biol. 145 (1990), 287-294.