So the Euclidean TSP decision problem is NP-complete (see http://dx.doi.org/10.1016/0304-3975(77)90012-3 ) so the TSP optimization problem should be NP-hard.
On the other hand there is a PTAS for the Euclidean TSP (see http://dx.doi.org/10.1145/290179.290180 ).
Wikipedia says that a PTAS is not possible for strongly NP-hard Problems.
So is this a contradiction, or is the Euclidean TSP "only" weakly NP-hard? Did I miss something else?