Michael C. Frank, Daniel L. Everett, Evelina Fedorenko and Edward Gibson: Number as a cognitive technology: Evidence from Pirahã language and cognition. Cognition, 2008, 108. vsk, nro 3, s. 819–824. doi:10.1016/j.cognition.2008.04.007Artikkelin verkkoversio. (englanniksi)
Michael C. Frank, Daniel L. Everett, Evelina Fedorenko and Edward Gibson: Number as a cognitive technology: Evidence from Pirahã language and cognition. Cognition, 2008, 108. vsk, nro 3, s. 819–824. doi:10.1016/j.cognition.2008.04.007Artikkelin verkkoversio. (englanniksi)