%0 Journal Article %A Nguyen, Viet Hung %T Approximation algorithms for metric tree cover and generalized tour and tree covers %J RAIRO - Operations Research - Recherche Opérationnelle %D 2007 %P 305-315 %V 41 %N 3 %I EDP-Sciences %U http://www.numdam.org/articles/10.1051/ro:2007025/ %R 10.1051/ro:2007025 %G en %F RO_2007__41_3_305_0