scheme and have been settled in [@quallbrunn]. In the case of codimension $1$ and $X={\mathbb{P}}^n$ there are several known examples of such components, the first known examples were established in [@jou] and up to the present is a very active research subject, in [@omegarlibro; @fj] one can find (non-exhaustive) lists of components. In the case of codimension $1$ and a general variety $X$ much less is known. In [@omegar] Calvo-Andrade proves that for a variety $X$ with $H^1(X,{\mathbb{C}})=0$ generic logarithmic $1$-forms give rise to integrable $1$-forms that are stable under small perturbations, *i.e.*: that there is an irreducible component of the space of integrable forms whose generic member defines a logarithmic foliation.

Besides stability, another important problem is the local and global characterization of the singularities of a foliation. Local results include the main theorems of [@malgrange] in codimension $1$ and of [@saito] and [@malgrange2] in higher codimension. Global studies have been made in the case of logarithmic foliations in [@fmi] and in the case of foliations defined by polynomial representations of affine lie algebras in [@ocgln] among others. An important type of singularity of a holomorphic foliation was discovered by Ivan Kupka in [@kupka]. A Kupka singularity for an 