Wiersma, William, author
Pearson/Allyn and Bacon, 2005
Buku Teks
Rummel, J. Francis
Harper & Row, 1964
Buku Teks
Best, John W.
Pearson, 2014
Buku Teks
Best, John W., author
Prentice Hall of India, 1982
Buku Teks
Ary, Donald, author
Usaha Nasional, 1982
Buku Teks