12 1 Introduction
http://www.utexas.edu/courses/bio301d/Topics/Scientific.method/
Text.html
http://www.w3.org/Math/
http://www.Warwick.ac.uk/staff/David.Tall/themes/proof.html
http://www.wmich.edu/math-stat/people/faculty/chartrand/proofs
http://www2.edc.org/makingmath/handbook/Teacher/Proof/Proof.asp
http://www2.edc.org/makingmath/mathtools/contradiction/
contradiction.asp
http://www2.edc.org/makingmath/mathtools/proof/proof.asp
https://www.theproofproj ect.org/bibliography/