Jakobsen, Jakob (1928–1932) [1921]. An etymological dictionary of the Norn language in Shetland (2 volumes). Printed by S. L. Møller, Copenhagen. Foreword by Anna Horsböl, née Jakobsen. Originally published in Danish as Etymologisk ordbog over det norröne sprog på Shetland. Reprinted Lerwick: The Shetland Folk Society, 1985. (1st ed.). Shaftesbury Avenue, London: David Nutt (A. G. Berry). pp. 24, 918. Retrieved 2020-03-24 – via archive.org.
Wells, J.V. (1994). "Correlates of the distribution and abundance of wintering gulls in Maine". Journal of Field Ornithology. 65 (3): 283–294. JSTOR4513942.
Karlsen, Rune Sveinsgjerd (27 January 2012). "Den tøffe måka og hauken" [The tough gull and the hawk] (in Norwegian). Natur i Bilder. Retrieved 28 June 2013.