Christoph Petz Jens Kasten Steffen Prohaska Hans-Christian Hege Hierarchical Vortex Regions in Swirling Flow. 863-870 2009 28 Comput. Graph. Forum 3 http://dx.doi.org/10.1111/j.1467-8659.2009.01463.x db/journals/cgf/cgf28.html#PetzKPH09