TY  - RPRT
TI  - The multi-slope model: A constructed stereoscopic model showing angles of slope from 2 to 90 degrees at different locations and sloping in different directions in the model
AU  - Robert J. Hackman
PY  - 1956
DO  - 10.3133/ofr5648
UR  - https://pubs.usgs.gov/publication/ofr5648
ID  - ofr5648
ER  -