References for "Proving Things: Analysis"
These are classics — probably available in
your local library. They are very different from each other.
George Polya, How to Solve It, Princeton University Press
(paperback)
George Polya, Mathematics and Plausible Reasoning, Volume 1:
Induction and Analogy in Mathematics
and Volume 2: Patterns of Plausible Inference, Princeton
University Press (paperback)
Richard Courant & Herbert Robbins, What Is Mathematics?,
Oxford University Press (paperback)
G. H. Hardy, A Course of Pure Mathematics, Cambridge
University Press (paperback).