Dong Zhang Depei Qian Weiguo Wu Ailong Liu Xuewei Yang Pen Han Spatial Map Data Share and Parallel Dissemination System Based on Distributed Network Services and Digital Watermark. 71-80 2007 conf/npc/2007 NPC http://dx.doi.org/10.1007/978-3-540-74784-0_8 db/conf/npc/npc2007.html#ZhangQWLYH07