Wild, John J.
Pearson, 2016
Buku Teks
editor, Oliva Blanchette, Tomonobu Imamich, George F. McLean, Togi M. P. Pangaribuan
The Council for Research in Values and Philosophy , 2001
Buku Teks SO
Blackwell, 2007
Buku Teks
IMF , 1999
Buku Teks
edited by Mario Telo
Springer, 2012
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