Knight-Jones, T. J. D.; Hauser, R.; Matthes, D.; Stärk, K. D. C.: Evaluation of effectiveness and efficiency of wild bird surveillance for avian influenza. Veterinary Research 41 (4), 50 (2010)
Scientists studying a rare population of tool-using chimpanzees have found that aging can have a profound impact on their abilities—but not all chimps decline equally.