Peter Keevash Benny Sudakov Set Systems with Restricted Cross-Intersections and the Minimum Rank of Inclusion Matrices. 713-727 2005 18 SIAM J. Discrete Math. 4 http://dx.doi.org/10.1137/S0895480103434634 db/journals/siamdm/siamdm18.html#KeevashS05