Hall, Kermit L.
Oxford University Press, 1991
Buku Teks
Hoffman, Herbert H.
Scarecrow Press, 1985
Buku Referensi
edited by Howard J. Wiarda, Harvey F. Kline
Westview Press, 2007
Buku Teks
Susana Nuccetelli, Ofelia Schutte, Otavio Bueno
Wiley, 2013
Buku Teks
Crawford, William R.
Frederick A. Praeger, 1961
Buku Teks