Stephen Cameron Tristam Fenton-May Joe Pitt-Francis Directions in the Use and Computation of Proximity Queries. 43-52 2002 conf/gmp/2002 GMP http://csdl.computer.org/comp/proceedings/gmp/2002/1674/00/16740043abs.htm db/conf/gmp/gmp2002.html#CameronFP02