Christopher B. Jones Ross Purves Anne Ruas Mark Sanderson Monika Sester Marc J. van Kreveld Robert Weibel Spatial information retrieval and geographical ontologies an overview of the SPIRIT project. 387-388 2002 conf/sigir/2002 SIGIR http://doi.acm.org/10.1145/564376.564457 db/conf/sigir/sigir2002.html#JonesPRSSKW02