Klein, Wolfgang
Routledge , 1997
Buku Teks
Hoff, Erika, 1951-, author
Wadsworth and Cengage Learning, 2014
Buku Teks
Crystal, David, 1941-, author
Cambridge University Press, 2005
Buku Teks
John E. Joseph, author
Edinburgh University Press, 2009
eBooks
edited by Joseph H. Greenberg
MIT Press, 1966
Buku Teks