APA (7th ed.) Citation

Webster, R., & Anderson, B. W. (1990). Gems: Their sources, descriptions and identification (4. ed.). Butterworths.

Chicago Style (17th ed.) Citation

Webster, Robert, and Basil W. Anderson. Gems: Their Sources, Descriptions and Identification. 4. ed. London [u.a.]: Butterworths, 1990.

MLA (9th ed.) Citation

Webster, Robert, and Basil W. Anderson. Gems: Their Sources, Descriptions and Identification. 4. ed. Butterworths, 1990.