Pinkney, Robert
Open University Press, 1993
Buku Teks
Calvocoressi, Peter
Longman, 1991
Buku Teks
Barke, Michael
Longman Scientific & Technical, 1991
Buku Teks
Calvocoressi, Peter
Longman, 1992
Buku Teks
Byrne, Jeffrey James
Oxford University Press, 2016
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