Leifer, Michael, author
Routledge, 1995
Buku Referensi
Leifer, Michael, author
Routledge, 1996
Buku Referensi
edited by Harold Brookfield and Yuonne Byron
United Nations University Press, 1993
Buku Teks
edited by John D. Montgomery, William J. Siffin
McGraw-Hill, 1966
Buku Teks
Cambridge University Press, 2010
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