Tansey, Stephen D., author
Routledge, 1996
Buku Teks
Combs, James E., author
Macmillan, 1984
Buku Teks
Eulau, Heinz, author
Bobbs-Merrill, 1963
Buku Teks
Dyke, Vernon van, author
Nelson, 1992
Buku Teks
Merriam, Charles E. (Charles Edward), author
University of Chicago Press, 1957
Buku Teks