Gauch, Hugh G., 1942-
Cambridge University Press, 2012
Buku Teks
Popper, Karl R.
Basic Books, 1959
Buku Teks
Gower, Barry
Routledge, 1997
Buku Teks
Morris, Richard
Simon and Schuster, 1983
Buku Referensi
E. David Ford
Cambridge University Press, 2000
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