http://www.worldwildlife.org/species/directory?sort=extinction_status
http://www.scientificamerican.com/slideshow/critically-endangered-species/
http://www.telegraph.co.uk/news/earth/wildlife/6927330/Top-10-most-endangered-species-in-the-world.html
http://www.mnn.com/earth-matters/animals/photos/10-animals-on-the-verge-of-extinction/polar-bears