Naoki Katoh, Taihei Yano. An approximation algorithm for the pickup and delivery vehicle routing problem on trees. Discrete Applied Mathematics, 154(16):2335-2349, 2006. [doi]
@article{KatohY06,
title = {An approximation algorithm for the pickup and delivery vehicle routing problem on trees},
author = {Naoki Katoh and Taihei Yano},
year = {2006},
doi = {10.1016/j.dam.2006.04.028},
url = {http://dx.doi.org/10.1016/j.dam.2006.04.028},
tags = {routing},
researchr = {https://researchr.org/publication/KatohY06},
cites = {0},
citedby = {0},
journal = {Discrete Applied Mathematics},
volume = {154},
number = {16},
pages = {2335-2349},
}