Benoit David Laurent Raynal Guylaine Schorter Véronique Mansart GeO2: Object-Oriented Contribution for a Geographical DBMS ? 377-383 1993 conf/dexa/1993 DEXA db/conf/dexa/dexa93.html#DavidRSM93 http://dx.doi.org/10.1007/3-540-57234-1_35