Whatmore, Richard, author
Polity, 2016
Buku Teks
Stromberg, Roland N.
Prentice-Hall, 1990
Buku Teks
Gordon, Andrew, author
Oxford University Press, 2003
Buku Teks
Murdoch, James, author
Routledge , 1926
Buku Referensi
Aczel, Tamas
Frederick A. Praeger, 1959
Buku Teks