Eley, B. M., author
Wright, 2004
Buku Teks
Jenkins, W.M., author
Wright , 1994
Buku Teks
Kieser, J. Bernard, author
Wright, 1990
Buku Teks
M.G.S, Prased, author
Lambert Ak\cademic Pblishing, 2012
Buku Teks
Allen, Don L., author
Lea & Febiger, 1980
Buku Teks