Pennings, Paul
Sage Publications, 1999
Buku Teks
Basil Gomez and John Paul Jones III, edited
Wiley-Blackwell, 2010
Buku Teks
Alston, Margaret, author
Allen & Unwin, 1998
Buku Teks
Lawrence R. Frey...[et al.]
Prentice-Hall, 1991
Buku Teks
Zechmeister, Eugene B., author
McGraw-Hill, 1992
Buku Teks