Peterson, Ivars (2005-04-01). "Sea Shell Spirals". Science News. Society for Science & the Public. Archived from the original on 2012-10-03. Retrieved 2011-12-14.
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Peterson, Ivars (2005-04-01). "Sea Shell Spirals". Science News. Society for Science & the Public. Archived from the original on 2012-10-03. Retrieved 2011-12-14.