| web | http://www.livescience.com/14819-crows-learn-dangerous-faces.html |
| author | Stephanie Pappas |
| publication | LiveScience |
| date | 2011-06-28 |
| web | New Scientist | 2010-01-26 | ||
| web | Michelle Nijhuis | New York Times | 2008-08-25 |
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