1. E. Grossman, As dairy farms grow bigger, new concerns about pollution. Yale Environ. 360 (2014). http://e360.yale.edu/feature/as_dairy_farms_grow_bigger_new_concerns_about_pollution/2768/ . Accessed April 2017.
2. USEPA, Inventory of U.S. Greenhouse Gas Emissions and Sinks: 1990-2009, EPA 430-R-11-005 (U.S. Environmental Protection Agency, Washington, DC, 2011).
3. J.A. Ogejo, Manure management and environmental stewardship, in Virginia Cooperative Extension (Publication, 2010), pp. 442–309.
4. S. Fields, Global nitrogen: cycling out of control. Environ. Health Perspect. 112, A556 (2004).
5. D.P.M. Zaks, N. Winchester, C.J. Kucharik, C.C. Barford, S. Paltsev, and J.M. Reilly, Contribution of anaerobic digesters to emissions mitigation and electricity generation under U.S. climate policy. Environ. Sci. Technol. 45, 6735 (2011).