What are your recommedations, all I could find in the local library is Introduction to Mathematical Logic by Mendelson, it is dated 1963, is that still ok? Is there any more state-of-the-art book on mathematical logic? I am interested in self-learning of mathematical logic. I would like to know a good source from where to study. One more thing, I noticed that prepositional calculus is in ways similar to boolean algebra, is there a formal relation between the two? Since I know from Digital Logic (and,or,xor, Karnough maps, Quinne-McCluskey method,...) some things in prepositional calculus are virtually the same as in boolean algebra. If there are soo similar why invent two systems, that would be like inventing n-tuple therory but as I recall the Set theory was reused to be used with n-tuples aswell, soo I would expect that there would be just prepositional caluclus or just boolean algebra but not both, but then again I am not good at Maths, just started to learn logic.