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2. Structure theory for geometric lattices;Crapo;Rend. Semin. Mat. Univ. Padova,1967
3. A lattice order on the set of all matroids on a set;Higgs;Canad. Math. Bull.,1966
4. Maps of geometries;Higgs;J. Lond. Math. Soc.,1966
5. Strong maps of geometries;Higgs;J. Combin. Theory,1968