Dimitris Papadias Man Lung Yiu Nikos Mamoulis Yufei Tao Nearest Neighbor Queries in Network Databases. 772-776 2008 Encyclopedia of GIS http://dx.doi.org/10.1007/978-0-387-35973-1_864 reference/gis/2008 db/reference/gis/gis2008.html#PapadiasYMT08