Gramberger, Marc, author
OECD, 2001
Buku Teks
Theodoulou, Stella Z., author
Thomson, 2004
Buku Teks
Sharkansky, Ira, author
Rand McNally College Publishing Company, 1975
Buku Teks
Molz, Redmond Kathleen, author
N.J Scarecroe Press, 1990
Buku Teks
Yannis Charalabidis, editor
Springer-Verlag, 2012
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