Citazione APA

Fraknoi, A., & Morrison, D. W. (2001). Voyages through the universe (2nd ed.). Harcourt College Publishers.

Stile di citazione Chicago

Fraknoi, Andrew, e David Wolff Morrison. Voyages Through the Universe. 2nd ed. Philadelphia: Harcourt College Publishers, 2001.

Citazione MLA

Fraknoi, Andrew, e David Wolff Morrison. Voyages Through the Universe. 2nd ed. Harcourt College Publishers, 2001.