Fraknoi, A., & Morrison, D. W. (2001). Voyages through the universe (2nd ed.). Harcourt College Publishers.
Chicago Edition CitationFraknoi, Andrew, i David Wolff Morrison. Voyages Through the Universe. 2nd ed. Philadelphia: Harcourt College Publishers, 2001.
Cita MLAFraknoi, Andrew, i David Wolff Morrison. Voyages Through the Universe. 2nd ed. Harcourt College Publishers, 2001.
Atenció: Aquestes cites poden no estar 100% correctes.