Invariants of transverse foliations (Q664664)

The paper under review considers transverse pairs of 1-dimensional foliations of \({\mathbb R}^2\). In [\textit{X.\ Wang}, On the \(C^*\)-Algebras of Foliations in the Plane. Lecture Notes in Mathematics, 1257. Berlin. Springer-Verlag. (1987; Zbl 0634.46052)] Wang associated an \({\mathbb R}\)-tree to any foliation \({\mathcal F}\) whose set of separatrices is Hausdorff in the leaf space \({\mathbb R}^2/{\mathcal F}\), and he proved that this \({\mathbb R}\)-tree determines the \(C^*\)-algebra of the foliation. In a similar spirit, the paper under review associates certain graphs to pairs of transverse foliations.