@article {15230,
	title = {Approximation algorithms with bounded performance guarantees for the clustered traveling salesman problem},
	journal = {Algorithmica},
	volume = {28},
	year = {2000},
	month = {2000///},
	pages = {422 - 437},
	abstract = {Let G=(V,E) be a complete undirected graph with vertex set V , edge set E , and edge weights l(e) satisfying triangle inequality. The vertex set V is partitioned into clusters V 1 , . . ., V k . The clustered traveling salesman problem is to compute a shortest Hamiltonian cycle (tour) that visits all the vertices, and in which the vertices of each cluster are visited consecutively. Since this problem is a generalization of the traveling salesman problem, it is NP-hard. In this paper we consider several variants of this basic problem and provide polynomial time approximation algorithms for them.},
	doi = {10.1007/s004530010045},
	author = {Guttmann-Beck,N. and Hassin,R. and Khuller, Samir and Raghavachari,B.}
}
