Unknown (juga dikenal sebagai Unknown Worlds) adalah sebuah majalah fiksi fantasi, yang diterbitkan dari 1939 sampai 1943 oleh Street & Smith, dan disunting oleh John W. Campbell. Unknown adalah sebuah penyertaan dari majalah fiksi ilmiah Street & Smith, Astounding Science Fiction, yang juga disunting oleh Campbell pada waktu itu; beberapa pengarang dan ilustrator berkontribusi pada kedua majalah tersebut.
- Ashley, Michael (1976) [First edition 1975]. The History of the Science Fiction Magazine Vol. 2 1936–1945. Chicago: Henry Regnery Company. ISBN 0-8092-8002-7.
- Ashley, Mike (2000). The Time Machines:The Story of the Science-Fiction Pulp Magazines from the beginning to 1950. Liverpool: Liverpool University Press. ISBN 0-85323-865-0.
- Asimov, Isaac (1979). In Memory Yet Green. Garden City, NY: Doubleday. ISBN 0-385-13679-X.
- Carter, Paul A. (1977). The Creation of Tomorrow: Fifty Years of Magazine Science Fiction. New York: Columbia University Press. ISBN 0-231-04211-6.
- Chapdelaine, Perry A.; Chapdelaine, Tony; Hay, George (1985). The John W. Campbell Letters: Volume 1. Franklin, TN: AC Projects. ISBN 0-931150-16-7.
- Clute, John; Grant, John (1997). The Encyclopedia of Fantasy. New York: St. Martin's Press, Inc. ISBN 0-312-15897-1.
- Clute, John; Nicholls, Peter (1993). The Encyclopedia of Science Fiction. New York: St. Martin's Press, Inc. ISBN 0-312-09618-6.
- Currey, Lloyd W. (1978). Science Fiction and Fantasy Authors: A Bibliography of First Printings of Their Fiction and Selected Nonfiction. Boston: G.K. Hall & Co. ISBN 0-8161-8242-6.
- del Rey, Lester (1979). The World of Science Fiction: 1926–1976: The History of a Subculture. New York: Ballantine Books. ISBN 0-345-25452-X.
- Hartwell, David G. (1987). The Dark Descent. New York: T. Doherty Associates. ISBN 0-312-93035-6.
- Kyle, David (1977). The Pictorial History of Science Fiction. London: Hamlyn. ISBN 0-600-38193-5.
- Tuck, Donald H. (1974). The Encyclopedia of Science Fiction and Fantasy. 1. Chicago: Advent: Publishers, Inc. ISBN 0-911682-20-1.
- Tuck, Donald H. (1982). The Encyclopedia of Science Fiction and Fantasy. 3. Chicago: Advent: Publishers, Inc. ISBN 0-911682-26-0.
- Tymn, Marshall B.; Ashley, Mike (1985). Science Fiction, Fantasy and Weird Fiction Magazines. Westport CT: Greenwood Press. ISBN 0-313-21221-X.