Litwack, L. F. (1961). North of slavery: The Negro in the free States, 1790-1860. University of Chicago Press.
Lua i Stíl Chicago (17ú heag.)Litwack, Leon F. North of Slavery: The Negro in the Free States, 1790-1860. [Chicago]: University of Chicago Press, 1961.
Lua MLA (9ú heag.)Litwack, Leon F. North of Slavery: The Negro in the Free States, 1790-1860. University of Chicago Press, 1961.
Rabhadh: Seans nach mbeach na luanna seo go hiomlán cruinn i ngach uile chás.