Some remarks for Oblig 2

The original formula F2 of Exercise O2.1 is not valid in classical logic. Oblig 2 has been updated with a correct (valid) version of F2; alternatively, you can provide a counter model or a failed proof for the original version of F2.

The supplementary material available at Supplementary Material for "Oblig 2" has been updated (and now includes a program frame for an implementation in Prolog).