Feith, Herbert
Equinox, 2007
Buku Teks
Cambridge University Press, 2019
eBooks
Caprara, Gian Vittorio, author
Oxford University Press, 2016
eBooks
Irish, Marian D., author
Prentice-Hall, 1962
Buku Teks
Smith, Christopher E.
Nelson-Hall Publishers, 1992
Buku Teks