Carter, K. L.; Robertson, B. C.; Kempenaers, B.: A differential DNA extraction method for sperm on the perivitelline membrane of avian eggs. Molecular Ecology 9 (12), pp. 2149 - 2150 (2000)
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.