MILP instances (in LP format) of the paper
Alberto Borghetti
A Mixed-Integer Linear Programming Approach for the Computation of the Minimum-Losses Radial Configuration of Electrical Distribution Networks
IEEE Transactions on Power Systems (Issue: 3, Aug. 2012, pp. 1264-1273)
https://doi.org/10.1109/TPWRS.2012.2184306
previously available at http://www.lisep.ing.unibo.it/optree.zip