This could have been invented by Raymond Smullyan http://en.wikipedia.org/wiki/Raymond_Smullyan#Logic_problems http://en.wikipedia.org/wiki/Raymond_Smullyan#Lo

This could have been invented by Raymond Smullyan http://en.wikipedia.org/wiki/Raymond_Smullyan#Logic_problems http://en.wikipedia.org/wiki/Raymond_Smullyan#Logic_problems