Hideki Hayashi Daisuke Ito Masaaki Tanizaki Kohji Kimura Hisanori Kajiyama Dual-heap <i>k</i>NN: <i>k</i>-nearest neighbor search for spatial data retrieval in embedded DBMS. 40 2008 GIS http://doi.acm.org/10.1145/1463434.1463484 conf/gis/2008 db/conf/gis/gis2008.html#HayashiITKK08