http://dx.doi.org/10.1007/3-540-48482-5_2 Timos K. Sellis Research Issues in Spatio-temporal Database Systems. 5-11 SSD/1999/16510005.pdf 1999 conf/ssd/99 SSD http://link.springer.de/link/service/series/0558/bibs/1651/16510005.htm db/conf/ssd/ssd99.html#Sellis99