@article{GDZPPN000363529,
title = {Steiner Minimal Trees on Sets of Four Points.},
journal = {Discrete \& computational geometry},
volume = {2},
year = {1987},
pages = {401-414},
zbl = {0623.05013},
url = {http://dml.mathdoc.fr/item/GDZPPN000363529}
}
Du, D.Z.; Hwang, F.K.; Song, G.D.; Ting, G.Y. Steiner Minimal Trees on Sets of Four Points.. Discrete & computational geometry, Tome 2 (1987) pp. 401-414. http://gdmltest.u-ga.fr/item/GDZPPN000363529/