Prins, Herschel
Routledge, 1995
Buku Teks
Sage, 1983
Buku Teks
Kelsen, Hans
Clarendon Press Oxford, 1992
Buku Teks
Brumfiel, Charles Francis, 1914-
California State Department of Education , 1965
Buku Teks SO
Cornman, James W.
Macmillan, 1968
Buku Teks SO