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researchgate.net
Alfrey, Peter; Legrand, Vincent. Azores Rare and Scarce Birds Report 2016(PDF) (Report). Azores Bird Club. p. 22. Archived(PDF) from the original on 25 November 2020. Retrieved 25 November 2020.
Alfrey, Peter; Legrand, Vincent. Azores Rare and Scarce Birds Report 2016(PDF) (Report). Azores Bird Club. p. 22. Archived(PDF) from the original on 25 November 2020. Retrieved 25 November 2020.