1. Research and Training Center on Disability in Rural Communities (RTC: Rural) Population Distribution by Urbanized Areas and Urban Clusters 2005 http://rtc.ruralinstitute.umt.edu/geography/docs/county3.pdf
2. US Census Bureau United States by Urban/Rural and Inside/Outside Metropolitan Area http://factfinder.census.gov/servlet/GCTTable?_bm=y&-geo_id=01000US&-_box_head_nbr=GCT-P1&-ds_name=DEC_2000_SF1_U&-redoLog=true&-format=US-1
3. US Census Bureau Detailed Tables: P2. Urban and Rural [6] - Universe: Total Population http://factfinder.census.gov/servlet/DTTable?_bm=y&-geo_id=01000US&-ds_name=DEC_2000_SF1_U&-_lang=en&-mt_name=DEC_2000_SF1_U_P002&-format=&-CONTEXT=dt
4. Defining the “rural” in rural America;Cromartie;Amber Waves,2008
5. USDA Measuring Rurality: Rural-Urban Continuum Codes. USDA Economic Research Service (ERS) http://www.ers.usda.gov/briefing/rurality/RuralUrbCon