Rossi, Renzo
Macmillan, 1996
Buku Referensi
Dixon, D. F.
Longman Cheshire , 1982
Buku Teks
McGraw-hill Open Univ. press , 2006
Buku Teks
Wilkinson, Caroline
Cambrigde University Press , 2008
Buku Teks
Wilkinson, Thomas O
The University of Massachusetts Press, 1965
Buku Teks