TY  - JOUR
A1  - Goodchild, M.F.
T1  - Citizens as sensors: The world of volunteered geography
Y1  - 2007
DO  - 10.1007/s10708-007-9111-y
JF  - GeoJournal
VL  - 69
IS  - 4
SP  - 211
EP  - -221

ER  -