Herbert Edelsbrunner John Harer Ajith Mascarenhas Valerio Pascucci Jack Snoeyink Time-varying Reeb graphs for continuous space-time data. 149-166 2008 41 Comput. Geom. 3 http://dx.doi.org/10.1016/j.comgeo.2007.11.001 db/journals/comgeo/comgeo41.html#EdelsbrunnerHMPS08