APA (7th ed.) Citation

Lopez, R. S. (1959). The tenth century: How dark the Dark Ages? Holt, Rinehart and Winston.

Chicago Style (17th ed.) Citation

Lopez, Robert S. The Tenth Century: How Dark the Dark Ages? New York: Holt, Rinehart and Winston, 1959.

MLA (9th ed.) Citation

Lopez, Robert S. The Tenth Century: How Dark the Dark Ages? Holt, Rinehart and Winston, 1959.