Mahood, H.R.
Pressure groups in American politics
Scribner, 1967
 Buku Teks SO
Michels, Robert, 1876-1936
Political Parties : a sociological study of the oligarchical tendencies of modern democracy
Collier Books, 1962
 Buku Teks SO
Klein, Josephine, 1926-
The study of groups
Routledge and Kegan Paul, 1956
 Buku Teks SO
Modern british poetry
edited by Louis Untermeyer
Harcourt, Brace, 1950
 Buku Teks SO
McKenzie, R.T.
British political parties the distribution of power within the conservative and labour parties
William Heinemann, 1955
 Buku Teks SO