Spanier, John W.
Praeger , 1967
Buku Teks
by Christopher S. Allen [and others]
D.C. Health, 1987
Buku Teks
Roberts, Geoffrey
Manchester University Press, 1984
Buku Teks
Tansey, Stephen D., author
Routledge, 1996
Buku Teks
Combs, James E., author
Macmillan, 1984
Buku Teks