Spyridon Antonakopoulos Chandra Chekuri F. Bruce Shepherd Lisa Zhang Buy-at-Bulk Network Design with Protection. 634-644 2007 FOCS http://doi.ieeecomputersociety.org/10.1109/FOCS.2007.17 conf/focs/2007 db/conf/focs/focs2007.html#AntonakopoulosCSZ07