Crawford, William R.
Frederick A. Praeger, 1961
Buku Teks
edited by Howard J. Wiarda, Harvey F. Kline
Westview Press, 2007
Buku Teks
Wynia, Gary W.
Cambridge University Press , 1984
Buku Teks
Wilgus, A. Curtis
Barner & Noble, 1963
Buku Teks
Susana Nuccetelli, Ofelia Schutte, Otavio Bueno
Wiley, 2013
Buku Teks