Euclidean Steiner Problem w/ duality

Hello,
I'm interested in learning more about the Euclidean Steiner Problem,
which asks: given a set of points in the plane (or any Euclidean
space), what is the point that minimizes the sum of the distances from
the given points to the chosen point? I am aware that the case is
solved using regular geometry for 3 given points, but I have also heard
that the problem can be solved using duality theory for any number of
points. Does anyone know where I can learn about such an approach?
Thanks!!!
KH

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