@inproceedings{g2005nl,
  title = {3D Screen-space Widgets for Non-linear Projection},
  author = {Leon Barrett and Patrick Coleman and Nisha Sudarsanam and Karan Singh and Cindy Grimm},
  booktitle = {Graphite},
  pages = {221-228},
  publisher = {ACM},
  note = {This paper lets the user specify multiple cameras using screen-space widgets.},
  month = {November},
  year = {2005}
}