Let be a codimension-one foliation, transversally oriented, of class on a connected closed manifold . The class of a leaf of is defined to be the union of all leaves with . Let be the space of classes of leaves in and let be the union of open subsets of which are homeomorphic to or to . In this paper we prove that if the level of is well defined (in the sense of ), then is a spectral space.
"Feuilletages et topologie spectrale." J. Math. Soc. Japan 52 (2) 447 - 464, April, 2000. https://doi.org/10.2969/jmsj/05220447