Litwack, L. F. (1961). North of slavery: The Negro in the free States, 1790-1860. University of Chicago Press.
芝加哥风格引文Litwack, Leon F. North of Slavery: The Negro in the Free States, 1790-1860. [Chicago]: University of Chicago Press, 1961.
MLA引文Litwack, Leon F. North of Slavery: The Negro in the Free States, 1790-1860. University of Chicago Press, 1961.
警告：这些引文格式不一定是100％准确.