Dyfyniad APA
Helgren, D. M., Sager, R. J., & Israel, S. (1985). World geography today. Holt, Rinehart and Winston.
Dyfyniad Arddull Chicago
Helgren, David M., Robert J. Sager, and Saul Israel. World Geography Today. New York: Holt, Rinehart and Winston, 1985.
Dyfyniad MLA
Helgren, David M., et al. World Geography Today. Holt, Rinehart and Winston, 1985.
Rhybudd: Mae'n bosib nad yw'r dyfyniadau hyn bob amser yn 100% cywir.