Seligman, Edwin R.A., author
Buku Teks
Seligman, Edwin R.A., author
Columbia University Press, 1949
Buku Teks
Steven & Sons, 1970
Buku Teks
Chesterman, Andrew, author
Cambridge University Press, 1991
Buku Teks
Batten,T.R., author
Oxford University Press, 1960
Buku Teks