@ARTICLE{Schulz2011a,
  author={Schulz, H.-J. and Hadlak, S. and Schumann, H.},
  journal={IEEE Transactions on Visualization and Computer Graphics},
  title={Point-Based Visualization for Large Hierarchies},
  year={2011},
  volume={17},
  number={5},
  pages={598--611},
  doi={10.1109/TVCG.2010.89},
}