1. Arnold, V.I.: Small denominators. I. On maps of the circle onto itself, Izv. Acad. Sc., USSR, Ser. Mat., 25, 1, 21?86 (1961)
2. Bott, R., Tu L.: Differential forms in algebraic topology G.T.M.82, Springer (1982)
3. Bredon, G.: Introduction to compact transformation groups, New York: Academic Press, 1972
4. El Kacimi Alaoui, A., Sergiescu, V., Hector, G., La cohomologie basique d'un feuilletage riemannien est de dimension finie, Math. Z.188, 593?599 (1985)
5. Haefliger, A.: Leaf closure in Riemannian foliations, A f�te on Topology. Papers dedicated to Itiro Tamura, London New York: Academic Press, 1988