Mayor, Frederico
UNESCO Publishing , 1999
Buku Teks
edited by John Corner, Sylvia Harvey
Routledge, 1991
Buku Teks
Phillips, Martin
Prentice-Hall, 2000
Buku Teks
Thomas F. King, editor
Wiley Blackwell, 2011
Buku Teks
edited by Marie Louise Sorensen and Dacia Viejo Rose
Cambridge University Press, 2015
Buku Teks