Alina Ene William G. Horne Nikola Milosavljevic Prasad Rao Robert Schreiber Robert Endre Tarjan Fast exact and heuristic methods for role minimization problems. 1-10 2008 SACMAT http://doi.acm.org/10.1145/1377836.1377838 conf/sacmat/2008 db/conf/sacmat/sacmat2008.html#EneHMRST08