Seeds, M. A., & Backman, D. E. (2012). Horizons: Exploring the universe (12th ed.). Brooks/Cole, Cengage Learning.
Dyfyniad Arddull ChicagoSeeds, Michael A., and Dana E. Backman. Horizons: Exploring the Universe. 12th ed. Australia, United States: Brooks/Cole, Cengage Learning, 2012.
Dyfyniad MLASeeds, Michael A., and Dana E. Backman. Horizons: Exploring the Universe. 12th ed. Brooks/Cole, Cengage Learning, 2012.
Rhybudd: Mae'n bosib nad yw'r dyfyniadau hyn bob amser yn 100% cywir.