https://www.amazon.com/Nuts-Bolts-Proofs-Introduction-Mathem... https://www.amazon.com/Art-Craft-Problem-Solving/dp/04717890...

See the following for general pointers. They may not be the exact material you want though.

http://www.artofproblemsolving.com/

http://www.amazon.com/Art-Craft-Problem-Solving/dp/047113571...

I wish I had access to people who were really good at problem solving when I was in my pre-university days. The intention is not to really become an ace problem solver, but to give the brain a real good workout.