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