the /solution/ tells us to ask "if you were to ask yourself which way to Vienna, what would you say?". I think that's a very bad quedstion: the liar (here he is called to be a knave) might think "the question ist way to vienna - I'm lying while asking, so I'd ask 'which is the way to [some place but vienna]?'". This makes the whole thing worthless. A lie isn't a boolean equation!
Plus, the question "Which is the road to Vienna" has lots of possible answers: Left, right, and "Back the way you came", for examples.
Really two? Maybe! Maybe? ;-)
the correct question to ask anyone of the 2 is:
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