Primary source: pmc.ncbi.nlm.nih.gov/articles/PMC243336/
Verified locator: Applied and Environmental Microbiology 37(5), 985–991 (1979), DOI 10.1128/aem.37.5.985-991.1979. Original initial-only bylines, USDA/University of Nebraska–Lincoln affiliation; Abstract, monitored bacterial indicators in grazed/ungrazed pasture runoff. No historical water-quality threshold imported.
Primary source: doi.org/10.2136/sssaj1984.03615995004800060013x
Verified locator: Soil Science Society of America Journal 48(6), 1267–1272 (1984), DOI 10.2136/sssaj1984.03615995004800060013x. Original Abstract and indexed publisher bylines D. M. Linn and J. W. Doran. Original scan downloads.regulations.gov/APHIS-2011-0023-0105/attachment_2.pdf . Laboratory response near 60% WFPS belongs to the studied conditions; no universal optimum asserted.