Herrmann, D. L., & Sally, P. J. (2013). Number shape symetry.
Chicago Edition CitationHerrmann, Diane L., and Paul J. Sally. Number Shape Symetry. CRC Press, London, 2013.
MLA Edition CitationHerrmann, Diane L., and Paul J. Sally. Number Shape Symetry. 2013.
Warning: These citations may not always be 100% accurate.