Polle Zellweger Niels Olof Bouvin Henning Qin Jehøj Jock D. Mackinlay Fluid annotations in an open world. 9-18 2001 conf/ht/2001 Hypertext http://doi.acm.org/10.1145/504216.504224 db/conf/ht/ht2001.html#ZellwegerBJM01