APA (7th ed.) Citation

Walker, С. В. F. (18). Halley's Comet in Babylonia.

Chicago Style (17th ed.) Citation

Walker, С. В. F. Halley's Comet in Babylonia. 18.

MLA (8th ed.) Citation

Walker, С. В. F. Halley's Comet in Babylonia. 18.

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