Arie Tamir Justo Puerto Juan A. Mesa Antonio M. Rodríguez-Chía Conditional location of path and tree shaped facilities on trees. 50-75 2005 56 J. Algorithms 1 http://dx.doi.org/10.1016/j.jalgor.2005.01.005 db/journals/jal/jal56.html#TamirPMR05