QPF A versatile query language for a knowledge-based geographical information system
1989 ◽
Vol 3
(1)
◽
pp. 51-57
◽
1987 ◽
Vol 1
(2)
◽
pp. 149-172
◽
1994 ◽
Vol 21
(2)
◽
pp. 179-190
◽
1993 ◽
Vol 4
(4)
◽
pp. 383-401
◽
1990 ◽
pp. 275-280
◽
2009 ◽
Vol 30
(24)
◽
pp. 6429-6440
◽
1994 ◽
Vol 5
(2)
◽
pp. 113-132
◽