Eagle, Lynne, author
Taylor & Francis Group, 2015
Buku Teks
Egan, John, 1952-
Thomson Learning,, 2007
Buku Teks
Egan, John, 1952-, author
Sage Publications, 2015
Buku Teks
Brierty, Edward G., author
Prentice-Hall, 1998
Buku Teks
Keegan, Warren J., author
Prentice Hall International, 1989
Buku Teks