@Article{RighSala06,
author = {G. Righini and Matteo Salani },
title = {Symmetry helps: Bounded bi-directional dynamic programming for the elementary shortest path problem with resource constraints},
journal = {Discrete Optimization},
volume = {3},
number = {3},
pages = {255-273},
doi = {10.1016/j.disopt.2006.05.007},
year = {2006}
}