Neumann, Victor, author
The Council for Research in Values and Philosophy , 2000
Buku Teks
Caminos, Hugo, author
United Kingdom Cambridge University Press, 2014
Buku Teks
Kandil, Hazem, author
Oxford University Press, 2016
eBooks
Stokes, Windy, author
Poloty Press, 2005
Buku Teks
Wang, James C.F., author
Prentice-Hall, 1985
Buku Teks