János Barát Leo Storme Multiple Blocking Sets in PG(<i>n</i>, <i>q</i>), <i>n</i>>3. 5-21 2004 33 Des. Codes Cryptography 1 http://dx.doi.org/10.1023/B:DESI.0000032603.40135.6b db/journals/dcc/dcc33.html#BaratS04