Mayo, Henry B.
Oxford University Press , 1960
Buku Teks
Sage Publications, 2012
eBooks
Dahl, Robert A., 1915-2014
The University of Chicago Press, 1956
Buku Teks
Cassinelli, C.W.
University of Washington Press , 1961
Buku Teks
Michael Saward, editor
Routledge, 2000
Buku Teks