@article {Karlen270, author = {Doug Karlen}, title = {Visual Soil Assessment., Volumes 1{\textendash}4}, volume = {56}, number = {4}, pages = {270--271}, year = {2001}, publisher = {Soil and Water Conservation Society}, issn = {0022-4561}, URL = {https://www.jswconline.org/content/56/4/270}, eprint = {https://www.jswconline.org/content/56/4/270.full.pdf}, journal = {Journal of Soil and Water Conservation} }