Fraknoi, A., & Morrison, D. W. (2001). Voyages through the universe (2nd ed.). Harcourt College Publishers.
Dyfyniad Arddull ChicagoFraknoi, Andrew, and David Wolff Morrison. Voyages Through the Universe. 2nd ed. Philadelphia: Harcourt College Publishers, 2001.
Dyfyniad MLAFraknoi, Andrew, and David Wolff Morrison. Voyages Through the Universe. 2nd ed. Harcourt College Publishers, 2001.
Rhybudd: Mae'n bosib nad yw'r dyfyniadau hyn bob amser yn 100% cywir.