Winterbotham, F. W. (1975). The Ultra secret. Dell Publishing Co.
Lua i Stíl Chicago (17ú heag.)Winterbotham, F. W. The Ultra Secret. New York: Dell Publishing Co, 1975.
Lua MLA (9ú heag.)Winterbotham, F. W. The Ultra Secret. Dell Publishing Co, 1975.
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