edited by Peter Moore, R.J. Berry and A. Hallam
Grolier International, 1993
Buku Referensi
McFarland, David
Longman, 1993
Buku Teks
Tullar, Richard M.
McGraw-Hill, 1977
Buku Teks
Facts on file, 1989
Buku Teks
Paterson, Hugh E
The Johns Hopkins University Press, 1992
Buku Teks