Goncalves, Rui Mario, author
Instituto de Cultura e Lingua Portuguesa, 1991
Buku Teks
Johnson, David W., 1940-, author
Allyn and Bacon, 1997
Buku Teks
Johnson, David W., 1940-, author
Allyn and Bacon, 2000
Buku Teks
Johnson, David W., 1940-, author
Pearson Education, 2006
Buku Teks
Hilger, M. Inez
The University of Oklahoma Press, 1971
Buku Teks