ATRACTOR

[1] Roger B. Nelsen, Proofs Without Words - Exercises in Visual Thinking, The Mathematical Association of America, 1993

[2] Roger B. Nelsen, Proofs Without Words II - Exercises in Visual Thinking, The Mathematical Association of America, 2000

[3] Reuben Hersh, Proving is convincing and explaining, in: Aspects of Proof, special volume of the journal Educational Studies in Mathematics, Vol. 24, N. 4, 1993

[4] Miguel de Guzmán, El papel de la visualizacion, in Laboratório de Matemáticas, Universidad Complutense de Madrid, 1996

[5] Burkard Polster, Q. E. D. - Beauty in Mathematical Proof, Walker & Company, 2004

[6] Claudi Alsina & Roger B. Nelsen, Math Made Visual - Creating Images for Understanding Mathematics, The Mathematical Association of America, 2006

[7] José Morgado, Equações do 2º grau ou Equações Quadráticas, in Millenium on.line (2º MatViseu), nº 16, 1999