template function w/ type & non-type parameters

I have the following class definitions:

template<unsigned dim>
class Vector
{ ... };

template<unsigned dim>
class Displacement : public Vector<dim>
{ ... };
template<unsigned dim>
class Velocity : public Vector<dim>
{ ... };
template<unsigned dim>
class Acceleration : public Vector<dim>
{ ... };

etc.

Now I want to overload binary operators +, - , *, /. But I don't want to write member functions for all vector types. (there are too many.) So I wrote the following template function:
      template<typename T, unsigned dim>
      T<dim> operator + (const T<dim> & t0, const T<dim> & t1)                 <<<< C2988 on this line
      {
            T<dim> ret;
            for (int i=0; i<dim; i++)
                  ret[i] = t0[i] + t1[i];
      }
But I get compiler error C2988 (unrecognizable template declaration/definition; Visual Studio Pro 2008). The help page (http://msdn.microsoft.com/en-us/library/f69a8fb8.aspx) is pretty useless.
Is it possible to write template like above (of course, w/o syntax errors) or do I have no choice but to copy-paste for all types derived from Vector<dim>?
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