Boughey, Arthur S.
McMillan Publisher, 1975
Buku Teks SO
Cambridge University Press, 2002
eBooks
Griffin, Ricky W.
Pearson Education International, 2006
Buku Teks
Griffin, Ricky W.
Prentice-Hall, 2002
Buku Teks
Wheeler, Bayard O.
Harper & Row. Publisher, 1968
Buku Teks