Rudolf Ahlswede Christian Bey Konrad Engel Levon H. Khachatrian The t-intersection Problem in the Truncated Boolean Lattice. 471-487 2002 23 Eur. J. Comb. 5 http://dx.doi.org/10.1006/eujc.2002.0590 db/journals/ejc/ejc23.html#AhlswedeBEK02