Retrieve coordinates of all selected vertices?

How can I program this?

I need to retrieve the global coordinates of all currently selected vertices.
With the list of the coords I would like to create a NURBS curve.

I found this:
But it prints ALL coordinates in the selected mesh.

Many thanks for your help!

ok; i FOUND IT:

So, now I have the coordinates in the Local Coordinate System…still have to find the way to transform these into the Global Coordinate System…

global_vec = obj.matrix_world * local_vec