Manachai Toahchoodee Indrakshi Ray On the Formal Analysis of a Spatio-temporal Role-Based Access Control Model. 17-32 2008 DBSec http://dx.doi.org/10.1007/978-3-540-70567-3_2 conf/dbsec/2008 db/conf/dbsec/dbsec2008.html#ToahchoodeeR08