1. A new quantitative method of topographic analysis;Chapman;American Journal of Science,1952
2. Qualifying relief terms;Drummond;Professional Geographer,1968
3. On the quantification of surface changes using grid-based Digital Elevation Models (DEMs);Etzelmüller;Transactions in GIS,2000
4. What do terrain statistics really mean?;Evans,1998
5. Statistical Analysis of Spherical Data;Fisher,1987