Chlepner, B.S.
Bookings Institution, 1943
Buku Teks
edited by Samir Mankabady
Croom Helm, 1984
Buku Teks
Lawlor, Alan
Macmillan Press , 1973
Buku Teks
Ross, Michael D.H.
MacDonald, 1960
Buku Teks
edited by Paul Taylor and A.J.R. Groom
Frances Pinter, 1978
Buku Teks