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Harper & Brothers Publishers, 1962
Buku Teks
Maton, Kenneth I., author
Oxford University Press, 2016
eBooks
Sabrina Chairunnisa, author
2016
Artikel Jurnal
Hanslove, Kurt L.
Cornell University , 1967
Buku Teks
R.Theodore Clark,Jr
The michie compony, 1991
Buku Teks