↑ No likeness or description of Euclid's physical appearance made during his lifetime survived antiquity. Therefore, Euclid's depiction in works of art depends on the artist's imagination (see Euclid).
↑ S. Dehaene; G. Dehaene-Lambertz; L. Cohen (Aug 1998). "Abstract representations of numbers in the animal and human brain". Trends in Neuroscience. 21 (8): 355–361. doi:10.1016/S0166-2236 (98) 01263-6 Check |doi= value (help). PMID9720604.
