Senelle, Robert
Ministry of Foreign Affairs and External Trade , 1979
Buku Teks
Godfrey, M.G.
Edward Arnold , 1986
Buku Teks
Presley, John W.
Prentice-Hall, 1982
Buku Teks
Hicks, John R.
Clarendon Press, 1959
Buku Teks
edited by Alice Horning and Anne Becker
Parlor Press, 2006
Buku Teks