Frank M. Shipman III J. Michael Moore Preetam Maloor Hao-wei Hsieh Raghu Akkapeddi Semantics happen: knowledge building in spatial hypertext. 25-34 2002 conf/ht/2002 Hypertext http://doi.acm.org/10.1145/513338.513350 db/conf/ht/ht2002.html#ShipmanMMHA02