Jim Lawrence. The odd-even invariant of an oriented matroid. Eur. J. Comb., 27(6):806-813, 2006. [doi]
@article{Lawrence06, title = {The odd-even invariant of an oriented matroid}, author = {Jim Lawrence}, year = {2006}, doi = {10.1016/j.ejc.2005.05.006}, url = {http://dx.doi.org/10.1016/j.ejc.2005.05.006}, researchr = {https://researchr.org/publication/Lawrence06}, cites = {0}, citedby = {0}, journal = {Eur. J. Comb.}, volume = {27}, number = {6}, pages = {806-813}, }