Pinkney, Robert
Open University Press, 1993
Buku Teks
Barke, Michael
Longman Scientific & Technical, 1991
Buku Teks SO
Barke, Michael
Longman Scientific & Technical, 1991
Buku Teks SO
Byrne, Jeffrey James
Oxford University Press, 2016
eBooks
Burnell, Peter J.
Westview Press, 1986
Buku Teks