@article {IOPORT.01347065,
    author       = {Anily, Shoshana and Bramel, Julien and Hertz, Alain},
    title        = {A $\frac{5}{3}$-approximation algorithm for the clusterd traveling salesman tour and path problems.},
    year         = {1999},
    journal      = {Operations Research Letters},
    volume       = {24},
    number       = {1-2},
    issn         = {0167-6377},
    pages        = {29-35},
    publisher    = {Elsevier Science Publishers (North-Holland), Amsterdam},
    doi          = {10.1016/S0167-6377(98)00046-7},
    abstract     = {Summary: We consider the Ordered Cluster Salesman Problem (OCTSP). In this problem, a vehicle starting and ending at a given depot must visit a set of $n$ points. The points are partitioned into $K$, $K\leq n$, prespecified clusters. The vehicle must first visit the points in cluster 1, then the points in cluster $2,\dots$, and finally the points in cluster $K$ so that the distance traveled is minimized. We present a $\frac 53$-approximation algorithm for this problem which runs in $O(n^3)$ time. We show that our algorithm can also be applied to the path version of the OCTSP: the ordered cluster traveling salesman path problem. Here the (different) starting and ending points of the vehicle may or may not be prespecified. For this problem, our algorithm is also a $\frac 53$-approximation algorithm.},
    identifier   = {01347065},
}