@inbook {DBLP:reference/db/Skiadopoulos18,
	title = {Cardinal Direction Relationships},
	booktitle = {Encyclopedia of Database Systems, Second Edition},
	year = {2018},
	doi = {10.1007/978-1-4614-8265-9_45},
	url = {https://doi.org/10.1007/978-1-4614-8265-9_45},
	author = {Spiros Skiadopoulos}
}
