Shoko Imaizumi, Masaaki Fujiyoshi, and Hitoshi Kiya,
“Efficient Collusion Attack-Free Access Control for Multidimensionally Hierarchical Scalability Content,”
inProc. of IEEE International Symposium on Circuits and Systems, no.A3L-F-4, pp.505-508, Taipei, Taiwan, R.O.C., 25th May, 2009.