(en-US) John Hope Franklin, From slavery to freedom : a history of Negro Americans, Vintage Books, , 772 p. (ISBN9780394704982, lire en ligne), p. 140
(en-US) Memorials presented to the Congress of the United States of America, by the different societies instituted for promoting the abolition of slavery, Francis Bailey, , 38 p. (lire en ligne)
(en-US) Gary M. Anderson, Charles K. Rowley & Robert D. Tollison, « Rent Seeking and the Restriction of Human Exchang », The Journal of Legal Studies, Vol. 17, No. 1, , p. 83-100 (18 pages) (lire en ligne)