1. W. Horsthemke and R. Lefever,“Noise-Induced Transitions”, Series in Synergetics (Springer-Verlag, New York). (To be published).
2. See the paper by J.M. Sancho and M. San Miguel in this volume.
3. M. San Miguel and J.M. Sancho in “Stochastic Nonlinear Systems”. Eds. L. Arnold and R. Lefever, Springer-Verlag (1981).
4. J.M. Sancho, M. San Miguel, S.L. Katz and J.D. Gunton, Phys. Rev. A26,1589 (1982).
5. A. Hernández-Machado and M. San Miguel, J. Math. Phys. (to appear).