editors of Ebony
Johnson Publishing Company, , 1966
Buku Referensi
Keeble, Richard, author
Routledge, 2007
Buku Referensi
Abbot, Waldo
McGraw-Hill, 1957
Buku Teks
Bender, James F.
Thomas Y. Cornell, 1951
Buku Teks
edited by John T. Daugirdas, Peter G. Blake, Todd S. Ing.
Wolters Kluwer, 2001
Buku Referensi