Babbie, Earl, author
Cengage Learning, 2016
Buku Teks
Laurene Vaughan
Bloomsbury Academic, 2017
Buku Teks
Hammersley, Martyn, author
Paul Chapman Publishing, 2002
Buku Teks
American Psychological Association, {s.a}
Majalah, Jurnal, Buletin
Hesse-Biber, Sharlene Nagy, author
Sage, 2007
Buku Teks