APA (7th ed.) Citation

Druce, G. C., Lumb, D., & Druce, G. C. (1922). Euphrasia septentrionalis ([Sonderdr.].).

Chicago Style (17th ed.) Citation

Druce, G. Claridge, D. Lumb, and G. Claridge Druce. Euphrasia Septentrionalis. [Sonderdr.]. 1922.

MLA (9th ed.) Citation

Druce, G. Claridge, et al. Euphrasia Septentrionalis. [Sonderdr.]. 1922.