Ola Ahlqvist Johannes Keukelaar Karim Oukbir Rough and fuzzy geographical data integration. 223-234 2003 17 International Journal of Geographical Information Science 3 http://taylorandfrancis.metapress.com/openurl.asp?genre=article&issn=1365-8816&volume=17&issue=3&spage=223 db/journals/gis/gis17.html#AhlqvistKO03