Birdsall, Stephen S.
John Wiley & Sons, 1992
Buku Teks SO
Johnston, R.J. (Ronald John)
Routledge, 2016
Buku Teks
Voice of America Forum Lectures , 1968
Buku Teks
Cohen, Saul B.
Vioce of America Forum Lectures , 1968
Buku Teks
Mittleman, Earl N.
New York University, [date of publication not identified]
Buku Teks