1. G. del Grosso, A. Gerardi, and F. Marchetti, A diffusion model for patch formation on cellular surfaces,Appl. Math Optim., this issue, 125?136.
2. E. B. Dynkin,Markov Processes, Chapter 2, Springer-Verlag, 1965.
3. A. Debiard, B. Gaveau, and E. Mazet, Th�oremes de comparison en g�ometrie riemannienne,Comptes Rendus Acad. Sciences Paris, Serie A, 281, 455?458 (1975).
4. I. Chavel, and D. Feldman, Spectra of domains in compact manifolds,Jour. Functional Analysis, 30, 198?222 (1978).
5. A. Levy-Bruhl, Courbure riemannienne et developpements infinitesimaux du Laplacien,Comptes Rendus Acad. Sciences Paris, Serie A, 279, 197?200 (1974).