1. USDA ERS (2015), U.S. milk production and related data,
http://www.ers.usda.gov
/data-products/dairy-data.aspx, June 25, 2015.
2. BSSC (2008). U.S. Dairy Sustainability Initiative: A roadmap to reduce greenhouse gas emissions and increase business value. Internet. Innovation Center for U.S. Dairy.
3. Liebrand C.B. & Ling K.C. (2009). Cooperative approaches for implementation of dairy manure digesters. In: (ed. USDA). USDA-Rural Development, p. 28.
4. USEPA (2014). Emissions & Generation Resource Integrated Database (eGRID) 9th edition Version 1.0 Year 2010 Summary Tables, updated 02/24/2014,
http://www.epa.gov
/cleanenergy/energy-resources/egrid/
5. USEPA (2011). Market Opportunities for Biogas Recovery Systems at U.S. Livestock Facilities. AgSTAR. Internet.