Office of the Secretary of State for Information and Tourism, [date of publication not identified]
Buku Teks
Birmingham, David
Cambridge University Press, 1993
Buku Teks
Disney, A.R
Cambridge University Press, 2009
Buku Teks
Torga, Miguel
Rua Cintura do Porto, 2003
Buku Referensi
by Carter J. Eckert ... [et.al.]
Korea Institute, Harvard University, 1990
Buku Teks