Recomendados:
[LC] Jon Barwise, John Etchemendy - Language, Proof and Logic @ http://ssdi.di.fct.unl.pt/~pb/cadeiras/lc/0102/lpl%20textbook.pdf
[LC] René Cori - Mathematical Logic: A course with exercises @ http://lix.in/-ad95d9
[LC] Shawn Hedman - A First Course in Logic @ http://lix.in/-bb516e
[LC] Michael Huth and Mark Ryan - Logic in Computer Science: modelling and reasoning about systems (2nd edition) @ http://www.eserna.com/Logica/5%20Lectura%202.pdf

Outros:
Mathematical Logic a course with exercices -----> http://min.us/mKt6ptJCX