Johnson LT, Tank JL, Dodds WK. The influence of land use on stream biofilm nutrient limitation across eight North American ecoregions. Canadian Journal of Fisheries and Aquatic Sciences. 2009;66:1081 -1094. doi:10.1139/F09-065.

Mulholland PJ, Hall RO, Sobota DJ, et al. Nitrate removal in stream ecosystems measured by 15N addition experiments: Denitrification. Limnology and Oceanography. 2009;54:666 -680. doi:10.4319/lo.2009.54.3.0666.

Hall, Jr. RO, Tank JL, Sobota DJ, et al. Nitrate removal in stream ecosystems measured by 15N addition experiments: Total uptake. Limnology and Oceanography. 2009;54:653 -665. doi:10.4319/lo.2009.54.3.0653.