References
- Ferens, B. 1962: Notes on the behaviour and activity of birds during the polar day in the Arctic. Zesz. Nauk. Uniw. Jagiell 50, Zool. 6. Kraków.
- Gullestad, N. 1977: Observasjoner av tyvjo (Stercorarius parasiticus) i Hornsund, Spitsbergen, 1963 og 1964. Nor. Polarinst. Arbok 1976, 371–373.
- Jakubiec, Z. 1982: A quantitative investigation on birds of the Hornsund Region, SW Spitsbergen. Acta Univ. Wratisl. 525 (4), 77-91. Wroclaw.