Circle

The missing piece

(by) Shel Silverstein.

Shapes: Triangles (Concepts)

Esther Sarfatti

Wing on a Flea a Book About Shapes

Ed Emberley

Circles: a mathematical view

D. Pedoe.

How Round Is Your Circle?: Where Engineering and Mathematics Meet

John Bryant, Chris Sangwin, John Bryant

The circle and the straight line

by John Harris.

Silly shapes: holes

[by Sophie Fatus].

Calling the circle: the first and future culture

Christina Baldwin.

Bruno Munari: square, circle, triangle

Bruno Munari ; [translation by] Maurizio Corraini

I see circles (First impressions)

Mike Artell