Schlesinger, Rudolf B.
The Foundation Press, 1950
Buku Teks
Pospisil, Leopold
Harper and Row Publisher, 1971
Buku Teks
Mark Tushnet
Foundation press, 1999
Buku Teks
Fox, James R.
Oceana Publications, Inc, 1992
Buku Teks
Hall, Jerome
Lousiana State University Press, 1963
Buku Teks