@Inproceedings{Lorentzos00,
author = {Lorentzos, N. A. and Tryfona, N. and Viqueira, J. R.},
title = {Relational Algebra for Spatial Data Management},
booktitle = {Proceedings of the International workshop on Integrated Spatial Databases, Digital Images and GIS (ISD'99) - LNCS 1737},
address = {Maine},
year = {2000},
}