Duffy, James
HArvard University Press, 1961
Buku Teks
Gunther, John, 1901-1970, author
Hamish Hamilon, 1955
Buku Teks
Busia, K.A.
Mouton, 1968
Buku Teks
edited by Olugbenga Adesida, Geci Karuri-Sebina, Joao Resende-Santos
Emerald, 2016
eBooks
Knapp, Rudiger, author
Fischer, 1973
Buku Teks