Tobias Polzin Siavash Vahdati Daneshmand Primal-Dual Approaches to the Steiner Problem Electronic Colloquium on Computational Complexity (ECCC) 2000 7 47 db/journals/eccc/eccc7.html#ECCC-TR00-047 http://eccc.hpi-web.de/eccc-reports/2000/TR00-047/index.html