M. Kazarian et al., CHARACTERISTIC CLASSES FOR THE DEGENERATIONS OF 2-PLANE FIELDS IN 4 DIMENSIONS, Pacific journal of mathematics, 179(2), 1997, pp. 355-370
Given a distribution of k-planes on a manifold, consider the degenerat
ion locus Sigma(I) consisting of points where the distribution has Lie
-bracket growth vector less than or equal I, a fixed integer vector. W
e calculate the characteristic classes associated to the Sigma(I) for
a generic two-plane distribution on a four-manifold.