edited by John Eatwell, Murray Milgate and Peter Newman
Macmillan, 1988
Buku Referensi
Nemmers, Erwin Esser
Littlefield, Adam and Co., 1960
Buku Teks
Johnson, Paul M.
Teraju, 2003
Buku Teks
Rutherford, Donald
Routledge, 1992
Buku Referensi
Johnson, Paul M.
Teraju, 2003
Buku Referensi