Shafer, Robert
[publisher not identified], [date of publication not identified]
Buku Teks
George, Robert Lloyd.
Woodhead Faulkner, 1992
Buku Teks
Kemp, Geoffrey
Brookings Institution Press, 1997
Buku Teks
Portland, Or. : F. Cass, 1995
Buku Teks
Taylor, C. Robert, author
Routledge, 1996
Buku Teks