Steiner Problem in Gromov-Hausdorff Space: the Case of Finite Metric   Spaces
  It is shown that each finite family of finite metric spaces, being considered as a subset of Gromov--Hausdorff space, can be connected by a Steiner minimal tree. 
Alexander Ivanov, Nadezhda Nikolaeva, Alexey Tuzhilin
math.MG