APA (7th ed.) Citation

Dal, B., & Morris, M. (1982). The butterflies of northern Europe. Croom Helm.

Chicago Style (17th ed.) Citation

Dal, Björn, and Michael Morris. The Butterflies of Northern Europe. London: Croom Helm, 1982.

MLA (9th ed.) Citation

Dal, Björn, and Michael Morris. The Butterflies of Northern Europe. Croom Helm, 1982.