Cita APA (7th ed.)

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

Cita Chicago (17th ed.)

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

Cita MLA (9th ed.)

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