Jan Terje Bjørke Stein Nilsen Wavelets applied to simplification of digital terrain models. 601-621 2003 17 International Journal of Geographical Information Science 7 http://taylorandfrancis.metapress.com/openurl.asp?genre=article&issn=1365-8816&volume=17&issue=7&spage=601 db/journals/gis/gis17.html#BjorkeN03