cliparts/5/f/2/0/clipart-optical-illusion-4-5f20.svg image/svg+xml Open Clip Art Library Optical Illusion (4) 2008-02-23T16:01:11 Jegorow, F.G. (1957). Militaerpsychologie. Berlin: Verlag des Ministeriums fuer nationale Verteidigung. http://openclipart.org/detail/14764/optical-illusion-(4)-by-cibo00-14764 cibo00 clip art clipart externalsource human perception human perception image media optical illusion optical illusion png pole pole public domain rope rope svg