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