APA (7th ed.) Citation

Ritz, M., Halle, S., Heckel, G., & Knijff, P. d. (2009). Speciation and hybridisation in skuas (Catharacta spp.).

Chicago Style (17th ed.) Citation

Ritz, Markus, Stefan Halle, Gerald Heckel, and Peter de Knijff. Speciation and Hybridisation in Skuas (Catharacta Spp.). 2009.

MLA (8th ed.) Citation

Ritz, Markus, et al. Speciation and Hybridisation in Skuas (Catharacta Spp.). 2009.