Karnaugh Map

Can get the concept from here

http://www.facstaff.bucknell.edu/mastascu/eLessonsHTML/Logic/Logic3.html

Use It After Testing

It is based in number system concept. Few errors have been injected. Use it only after testing-- white box or black box.
http://www.scribd.com/doc/28072106/

This is an interseting white paper on Users Acceptance Testing describing some common scenario.

http://www.infosentry.com/uatp_lessons_learned.pdf

What is Software Testing?

Following link takes you to a page where Software Testing concept is put in summerised and simple way.

http://www.ece.cmu.edu/~koopman/des_s99/sw_testing/