M. Barnabei, G. Nicoletti, Axiomatizing Matroids by Means of the Set of Non-Generators, to appear in Boll. U.M.I.
T.H. Brylawski, An Outline for the Study of Combinatorial Pregeometries, Lecture Note Series, University of North Carolina, Chapel Hill, 1972.
H.H. Crapo, G.C. Rota, On the Foundations of Combinatorial Theory: Combinatorial Geometries, M.I.T. Press, Cambridge, Mass., 1970.
D.J.A. Welsh, Matroid Theory, Academic Press, London, 1976.