United States. Census Office. 6th Census, 1840, & United States. National Archives and Records Service. (1973). Schedule of mines, agriculture, commerce, manufactures, etc. of 1840 census for Illinois. National Archives.
Chicago-referens (17:e uppl.)United States. Census Office. 6th Census, 1840, och United States. National Archives and Records Service. Schedule of Mines, Agriculture, Commerce, Manufactures, Etc. of 1840 Census for Illinois. Washington, D.C.: National Archives, 1973.
MLA-referens (8:e uppl.)United States. Census Office. 6th Census, 1840, och United States. National Archives and Records Service. Schedule of Mines, Agriculture, Commerce, Manufactures, Etc. of 1840 Census for Illinois. National Archives, 1973.
Varning: dessa hänvisningar är inte alltid fullständigt riktiga.