Adams, James E.
Wiley-Blackwell, 2009
Buku Teks
edited by Patrick Brantlinger and William B. Thesing
Blackwell, 2002
Buku Referensi
Banks, J.A.
Routledge & Kegan Paul, 1954
Buku Teks SO
edited by Gordon Marsden
Longman, 1990
Buku Teks SO
Nattrass, Laonora
Cambridge University Press, 2003
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