Blackwell Publishing, 2007
Buku Teks
Lodico, Marguerite G., author
Jossey-Bass, 2010
Buku Teks
Stake, Robert E.
Sage Publications, 1995
Buku Teks
Clough, Peter, author
Sage Publications, 2002
Buku Referensi
Fraenkel, Jack R., 1932-2014, author
McGraw-Hill, 1993
Buku Teks