soneto

http://theby.blogspot.com/

modal logic

http://philosophy.ucdavis.edu/mattey/phi134/index.htm

Heck - Frege

http://frege.brown.edu/heck/philosophy/index.php

http://frege.brown.edu/heck/pdf/published/FregeContribution.pdf

Provador de teoremas

http://www.umsu.de/logik/trees/