[1][neaktivna poveznica] A. J. Sillman, D. A. Bolnick, L. W. Haynes, A. E. Walter and E. R. Loew: Microspectrophotometry of the photoreceptors of palaeognathous birds — the emu and the tinamou. Journal of Comparative Physiology A: Neuroethology, Sensory, Neural, and Behavioral Physiology. S. 271-276 Volume 144, Number 3 / September 1981. DOI 10.1007/BF00612558.
