Nowell, C. E. (1973). Portugal. Prentice-Hall, Inc.
Lua i Stíl Chicago (17ú heag.)Nowell, Charles E. Portugal. Englewood Cliffs, New Jersey: Prentice-Hall, Inc, 1973.
Lua MLA (9ú heag.)Nowell, Charles E. Portugal. Prentice-Hall, Inc, 1973.
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