Item from Mathematical Reviews (American Mathematical Society)--access
their stable url through the AMS database via an institutional library:
MR1460670 (98e:90087) Fliege, J. Nondifferentiability detection and
dimensionality reduction in minisum multifacility location problems. J.
Optim. Theory Appl. 94 (1997), no. 2, 365--380. (Reviewer: Sandra L.
Arlinghaus) 90B80 (90C30)