Kevin Buchin Tamal K. Dey Joachim Giesen Matthias John Recursive geometry of the flow complex and topology of the flow complex filtration. 115-137 2008 40 Comput. Geom. 2 http://dx.doi.org/10.1016/j.comgeo.2007.05.005 db/journals/comgeo/comgeo40.html#BuchinDGJ08