Sharkansky, Ira, author
Rand McNally College Publishing Company, 1975
Buku Teks
Eropa Local Government Center, 1993
Buku Teks
Chapman, Brian
Allen & Unwin, 1966
Buku Teks
Herring, E. Pendleton, author
McGraw-Hill, 1936
Buku Teks
Simon, Herbert A., author
Alfred A. Knopf, 1973
Buku Teks