@article{DCG_1993__9_2_131252,
     author = {Ding-Zhu Du and Biao Gao and R. L. Graham and Zi-Cheng Liu and Peng-Jun Wan},
     title = {Minimum {Steiner} {Trees} in {Normed} {Planes.}},
     journal = {Discrete & computational geometry},
     pages = {351--370},
     publisher = {mathdoc},
     volume = {9},
     number = {2},
     year = {1993},
     zbl = {0774.05028},
     url = {http://geodesic.mathdoc.fr/item/DCG_1993__9_2_131252/}
}