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-viite (17. p.)United States. Census Office. 6th Census, 1840, ja 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-viite (8. p.)United States. Census Office. 6th Census, 1840, ja United States. National Archives and Records Service. Schedule of Mines, Agriculture, Commerce, Manufactures, Etc. of 1840 Census for Illinois. National Archives, 1973.
Varoitus: Nämä viitteet eivät aina ole täysin luotettavia.