The index set problem for Boolean (or nonnegative) matrices.

Qiao Li Jiayu Shao The index set problem for Boolean (or nonnegative) matrices. 75-92 1993 123 Discrete Mathematics 1-3 http://dx.doi.org/10.1016/0012-365X(93)90008-H db/journals/dm/dm123.html#LiS93