An Orlik-Solomon type algebra for matroids with a fixed linear class of   circuits
  A family C of circuits of a matroid M is a linear class if, given a modular pair of circuits in C}, any circuit contained in the union of the pair is also in C. The pair (M,C) can be seen as a matroidal generalization of a biased graph. We introduce and study an Orlik-Solomon type algebra determined by (M,C). If C is the set of all circuits of M this algebra is the Orlik-Solomon algebra of M. 
Raul Cordovil (IST, Portugal), David Forge (LRI (Orsay), France)