1. E. Babson, D.N. Kozlov, Proof of the Lovász conjecture, Ann. of Math. (2) (in press).http://www.arxiv.org/abs/math/0402395
2. Topological methods;Björner,1995
3. Chessboard complexes and matching complexes;Björner;J. London Math. Soc.,1994
4. A. Engström, Complexes of directed trees and independence complexes. http://www.arxiv.org/abs/math/0508148
5. Complexes of directed trees;Kozlov;J. Combin. Theory Ser. A,1999