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The New Dutch Timetable
In December 2006, Netherlands Railways introduced a completely new timetable. Its objective was to facilitate the growth of passenger and freight transport on a highly utilized railway network and ...
On the history of the transportation and maximum flow problems
We review two papers that are of historical interest for combinatorial optimization: an article of A.N. Tolstoi from 1930, in which the transportation problem is studied, and a negative cycl...
Making Curves Minimally Crossing by Reidemeister Moves
LetC1, , Ckbe a system of closed curves on a triangulizable surfaceS. The system is calledminimally crossingif each curveCihas a minimal number of self-intersections among all curvesC ifreely homot...
Equilateral Dimension of the Rectilinear Space
It is conjectured that there exist at most 2k equidistant points in the k -dimensional rectilinear space. This conjecture has been verified for k\leq 3 ; we show here its validity in dimension k=4 ...