Polman, Katrien
The Hague Martinus Nijhoff, 1981
Buku Referensi
Gershoy, Leo, author
Appleton Century Crofts, 1964
Buku Teks
Orta, John, author
Garland Publishing, 1988
Buku Referensi
Hurt, R. Douglas, author
Garland Publishing, 1994
Buku Referensi
Rothschild, Bruce M., author
Springer, 2012
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