\begin{thebibliography}{10}

\bibitem{bg89:tsnp}
M.W. Bern and R.L. Graham.
\newblock The shortest-network problem.
\newblock {\em Sci. Am.}, 260(1):84--89, January 1989.

\bibitem{bs75:aivocspsftmnp}
W.M. Boyce and J.R. Seery.
\newblock {STEINER} 72 -- an improved version of {C}ockayne and {S}chiller's
  program {STEINER} for the minimal network problem.
\newblock Technical Report~35, Bell Labs., Dept. of Computer Science, 1975.

\bibitem{cockayne67:otsp}
E.J. Cockayne.
\newblock On the {S}teiner problem.
\newblock {\em Canad. Math. Bull.}, 10(3):431--450, 1967.

\bibitem{cockayne70:oteotafsmt}
E.J. Cockayne.
\newblock On the efficiency of the algorithm for {S}teiner minimal trees.
\newblock {\em SIAM J. Appl. Math.}, 18(1):150--159, January 1970.

\bibitem{ch86:ecosmtitp}
E.J. Cockayne and D.E. Hewgill.
\newblock Exact computation of {S}teiner minimal trees in the plane.
\newblock {\em Info. Proc. Lett.}, 22(3):151--156, March 1986.

\bibitem{ch92:icopsmt}
E.J. Cockayne and D.E. Hewgill.
\newblock Improved computation of plane {S}teiner minimal trees.
\newblock {\em Algorithmica}, 7(2/3):219--229, 1992.

\bibitem{cs72:cosmt}
E.J. Cockayne and D.G. Schiller.
\newblock Computation of {S}teiner minimal trees.
\newblock In D.J.A. Welsh and D.R. Woodall, editors, {\em Combinatorics}, pages
  52--71. Inst. Math. Appl., Southend-on-Sea, 1972.

\bibitem{cr41:wim}
R.~Courant and H.~Robbins.
\newblock {\em What is Mathematics}.
\newblock Oxford University Press, London, 1941.

\bibitem{dh92:apotgpcotsr}
D.Z. Du and F.H. Hwang.
\newblock A proof of the {G}ilbert-{P}ollak conjecture on the {S}teiner ratio.
\newblock {\em Algorithmica}, 7(2/3):121--135, 1992.

\bibitem{ggj77:tcocsmt}
M.R. Garey, R.L. Graham, and D.S Johnson.
\newblock The complexity of computing {S}teiner minimal trees.
\newblock {\em SIAM J. Appl. Math.}, 32:835--859, 1977.

\bibitem{gp68:smt}
E.N. Gilbert and H.O. Pollak.
\newblock Steiner minimal trees.
\newblock {\em SIAM J. Appl. Math.}, 16(1):1--29, 1968.

\bibitem{hr92:survey}
F.K. Hwang and D.S. Richards.
\newblock Steiner tree problems.
\newblock {\em Networks}, 22(1):55--89, January 1992.

\bibitem{hstd88:adtoesmt}
F.K. Hwang, G.D. Song, G.Y. Ting, and D.Z. Du.
\newblock A decomposition theorem on {E}uclidian {S}teiner minimal trees.
\newblock {\em Disc. Comput. Geom.}, 3(4):367--382, 1988.

\bibitem{hw86:hcsasmt}
F.K. Hwang and J.F. Weng.
\newblock Hexagonal coordinate systems and {S}teiner minimal trees.
\newblock {\em Disc. Math.}, 62(1):49--57, October 1986.

\bibitem{jk34:omgodb}
V.~{Jarn\'{i}k} and O~{K\"{o}ssler}.
\newblock O minim\'{a}lnich gratech obsahujicich n dan\'{y}ch bodu [in
  {C}zech].
\newblock {\em Casopis Pesk. Mat. Fyr.}, 63:223--235, 1934.

\bibitem{melzak61:otpos}
Z.A. Melzak.
\newblock On the problem of {S}teiner.
\newblock {\em Canad. Math. Bull.}, 4(2):143--150, 1961.

\bibitem{winter85:aaftspitep}
P.~Winter.
\newblock An algorithm for the {S}teiner problem in the {E}uclidian plane.
\newblock {\em Networks}, 15(3):323--345, Fall 1985.

\end{thebibliography}
