|title=The Geometry and Pigmentation of Seashells |author= Coombs, Stephen |year=2009 |url=http://www.maths.nott.ac.uk/personal/sc/pdfs/Seashells09.pdf}}</ref>
|title=The Geometry and Pigmentation of Seashells |author= Coombs, Stephen |year=2009 |url=http://www.maths.nott.ac.uk/personal/sc/pdfs/Seashells09.pdf}}</ref>