Wiersma, William, author
Pearson/Allyn and Bacon, 2005
Buku Teks
Ary, Donald
Wardsword Cengage Learning, 2010
Buku Teks
Wiersma, William, author
Pearson, 2009
Buku Teks
Wiersma, William
Allyn and Bacon , 1991
Buku Teks
Rummel, J. Francis
Harper & Row, 1964
Buku Teks