@article{DBLP:journals/aei/BorrmannR09,
author = {Andr{\'e} Borrmann and
Ernst Rank},
title = {Specification and implementation of directional operators
in a 3D spatial query language for building information
models},
journal = {Advanced Engineering Informatics},
volume = {23},
number = {1},
year = {2009},
pages = {32-44},
ee = {http://dx.doi.org/10.1016/j.aei.2008.06.005},
bibsource = {DBLP, http://dblp.uni-trier.de}
}