APA (7th ed.) Citation

Petersen, Æ., Petersen, A., & Perrins, C. (1981). Breeding biology and feeding ecology of Black guillemots.

Chicago Style (17th ed.) Citation

Petersen, Æ, Aevar Petersen, and C. Perrins. Breeding Biology and Feeding Ecology of Black Guillemots. 1981.

MLA (9th ed.) Citation

Petersen, Æ, et al. Breeding Biology and Feeding Ecology of Black Guillemots. 1981.