Weiping Shi, Chen Su. The rectilinear Steiner arborescence problem is NP-complete. In SODA. pages 780-787, 2000. [doi]
@inproceedings{ShiS00:0,
title = {The rectilinear Steiner arborescence problem is NP-complete},
author = {Weiping Shi and Chen Su},
year = {2000},
doi = {10.1145/338219.338639},
url = {http://doi.acm.org/10.1145/338219.338639},
tags = {completeness},
researchr = {https://researchr.org/publication/ShiS00%3A0},
cites = {0},
citedby = {0},
pages = {780-787},
booktitle = {SODA},
}