Serafino Cicerone Daniele Frigioni Laura Tarantino Paolino Di Felice Interacting with Topological Invariants of Spatial Databases. 213-217 1999 conf/dante/1999 DANTE http://csdl.computer.org/comp/proceedings/dante/1999/0496/00/04960213abs.htm db/conf/dante/dante1999.html#CiceroneFTF99