APA (7th ed.) Citation

Bullough, W. S., & Bullough, H. (1954). Introducing animals with backbones. Mathuen.

Chicago Style (17th ed.) Citation

Bullough, William Sydney, and Helena Bullough. Introducing Animals with Backbones. London: Mathuen, 1954.

MLA (9th ed.) Citation

Bullough, William Sydney, and Helena Bullough. Introducing Animals with Backbones. Mathuen, 1954.