Item from Mathematical Reviews (American Mathematical Society)--access
their stable url through the AMS database via an institutional library:
MR1791201 (2001g:90029) Bandelt, Hans-Jürgen; Chepoi, Victor;
Karzanov, Alexander A characterization of minimizable metrics in the
multifacility location problem. Discrete metric spaces (Marseille,
1998). European J. Combin. 21 (2000), no. 6, 715--725. (Reviewer:
Sandra L. Arlinghaus) 90B80 (05C12)