Smalley, Ruth Elizabeth, author
Columbia University Press, 1971
Buku Teks
Musson, Philip, author
Learning Matters, 2011
Buku Teks
Field, Richard, author
Learning Matters,, 2012
Buku Teks
Keefe, Robert H., author
Springer Publishing Company, 2013
Buku Teks
Thyer, Bruce A.
London : Sage Publications, 2001,
Buku Referensi