Satoru Fujishige Gleb A. Koshevoy Yoshio Sano Matroids on convex geometries (cg-matroids). 1936-1950 2007 307 Discrete Mathematics 15 http://dx.doi.org/10.1016/j.disc.2006.09.037 db/journals/dm/dm307.html#FujishigeKS07