Barker, Chris, author
John Wiley & Sons, 2002
Buku Teks
Saunders, Mark, author
Pearson Education, 2016
Buku Teks
Saunders, Mark, author
Prentice-Hall, 2003
Buku Teks
Wiersma, William, author
Pearson/Allyn and Bacon, 2005
Buku Teks
Wiersma, William, author
Pearson, 2009
Buku Teks