Widdowson, H.G., author
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Buku Teks
Salkie, Raphael
London, 1995
Buku Teks
Dijk, Teun A. van, 1943-, author
Longman, 1992
Buku Teks
Baka, Farida, author
Janus Publishing , 1988
Buku Teks
Journal of Population, Vol 1 No. 1 June 1995 : 71-103, 1995
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