Stefan Burkhardt Juha Kärkkäinen Better Filtering with Gapped q-Grams. 51-70 2003 56 Fundam. Inform. 1-2 http://iospress.metapress.com/openurl.asp?genre=article&issn=0169-2968&volume=56&issue=1&spage=51 db/journals/fuin/fuin56.html#BurkhardtK03