1. Lobbying in the United States. Available at: http://en.wikipedia.org/wiki/Lobbying_in_the_United_States.
2. Lobbying Issues. http://www.irs.gov/pub/irs-tege/eotopicp97.pdf.
3. Federal Lobbying: Differences in Lobbying Definitions and Their Impact. Available at: http://www.gpo.gov/fdsys/pkg/GAOREPORTS-GGD-99-38/html/GAOREPORTS-GGD-99-38.htm.
4. Hrebenar RJ, Morgan B. Lobbying in America. ABC-CLIO,. ISBN 978-1-59884-112-1, 2009.
5. Federalist. Available at: http://en.wikisource.org/wiki/Page:Federalist,_Dawson_edition,_1863.djvu/202.