Ballast, David Kent, author
Professional Publications, Inc., 2002
Buku Referensi
Wiley, 1995
Buku Teks
Burt, William Henry, author
Houghton Miffiln, 1976
Buku Referensi
Paludi, Michele Antoinette
Albany State University of New York Press 1991,
Buku Teks
Fishkin, Rand, author
Penguin, 2018
Buku Teks