"What to see". www.gibraltar.gov.uk. Archived from the original on 4 November 2011. Retrieved 28 October 2012.
gonhs.org
Charles Perez & Keith Bensusan (2005). "A Guide to The Upper Rock Nature Reserve"(PDF). The Gibraltar Ornithologicaland Natural History Society. Archived from the original(PDF) on 10 May 2013. Retrieved 28 October 2012.
Charles Perez & Keith Bensusan (2005). "A Guide to The Upper Rock Nature Reserve"(PDF). The Gibraltar Ornithologicaland Natural History Society. Archived from the original(PDF) on 10 May 2013. Retrieved 28 October 2012.