Jan Sahner Tino Weinkauf Nathalie Teuber Hans-Christian Hege Vortex and Strain Skeletons in Eulerian and Lagrangian Frames. 980-990 2007 13 IEEE Trans. Vis. Comput. Graph. 5 http://doi.ieeecomputersociety.org/10.1109/TVCG.2007.1053 db/journals/tvcg/tvcg13.html#SahnerWTH07