Blythe, Jim, author
Prentice-Hall, 2000
Buku Teks
Eagle, Lynne, author
Taylor & Francis Group, 2015
Buku Teks
Egan, John, 1952-, author
Sage Publications, 2015
Buku Teks
Egan, John, 1952-
Thomson Learning,, 2007
Buku Teks
Belch, George E., author
McGraw-Hill, [date of publication not identified]
Buku Referensi