Smith, G.M.; Fuller, R.M.; Costa, C.; Devereux, B.J.: 'An integrated vector/raster system for land cover mapping', IET Conference Proceedings, 1998, p. 2-2, DOI: 10.1049/ic:19980087
IET Digital Library, https://digital-library.theiet.org/;jsessionid=1iaecj1diaac.x-iet-live-01content/conferences/10.1049/ic_19980087