Paul H. Edelman, Victor Reiner, Volkmar Welker. Convex, Acyclic, and Free Sets of an Oriented Matroid. Discrete & Computational Geometry, 27(1):99-116, 2002. [doi]
@article{EdelmanRW02,
title = {Convex, Acyclic, and Free Sets of an Oriented Matroid},
author = {Paul H. Edelman and Victor Reiner and Volkmar Welker},
year = {2002},
url = {http://link.springer.de/link/service/journals/00454/contents/01/0055/},
researchr = {https://researchr.org/publication/EdelmanRW02},
cites = {0},
citedby = {0},
journal = {Discrete & Computational Geometry},
volume = {27},
number = {1},
pages = {99-116},
}