Cassidy, Harold G.
Freeman, Cooper & Company , 1970
Buku Teks SO
Butler, Stuart Thomas
Horwitz-Grahame, 1960
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Taylor and Francis, 2000
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Wendy Brown ... [and others] ; edited by Jonathan Ling
Longman Singapore Publishers, 1995
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Butt, Hans-Jurgen
Wiley-VCH Verlag, 2013
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