Mountford, James, Sir, author
Oxford Unniversity Press, 1966
Buku Teks
UK : The Association of Commonwealth Universities, 1988,
Buku Referensi
Meister, Jeanne C
McGraw-Hill, Inc, 1998
Buku Teks
O`Leary, John, author
QS Quacquarelli Symonds Limited, 2010
Buku Referensi
Feingold, Mordechai, author
Oxford University Press, 2017
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