Artikel Jurnal
Saville-Troike, Muriel, 1936-, author
Cambridge University Press , 2006
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Saville-Troike, Muriel, 1936-, author
Cambridge University Press, 2012
Buku Teks
Larsen-Freeman, Diane
Longman , 1992
Buku Teks
Ellis, Rob, author
Blackwell, 1990
Buku Teks