@inbook {DBLP:reference/db/Skiadopoulos09,
	title = {Cardinal Direction Relationships},
	booktitle = {Encyclopedia of Database Systems},
	year = {2009},
	pages = {305{\textendash}308},
	doi = {10.1007/978-0-387-39940-9_45},
	url = {https://doi.org/10.1007/978-0-387-39940-9_45},
	author = {Spiros Skiadopoulos}
}
