APA (7th ed.) Citation

Stone, D. M., & Butt, R. A. (1972). A guide to Australian precious opal. Periwinkle Books.

Chicago Style (17th ed.) Citation

Stone, Douglas M., and Robert A. Butt. A Guide to Australian Precious Opal. Melbourne: Periwinkle Books, 1972.

MLA (8th ed.) Citation

Stone, Douglas M., and Robert A. Butt. A Guide to Australian Precious Opal. Periwinkle Books, 1972.

Warning: These citations may not always be 100% accurate.