@article{improvedwideanglefisheyeand,
  title = {Improved wide-angle, fisheye and omnidirectional camera calibration},
  author = {Steffen Urban and Jens Leitloff and Stefan Hinz},
  year = {2015},
  url = {https://www.ipf.kit.edu/downloads/Preprint_ImprovedWideAngleFisheyeAndOmnidirectionalCameraCalibration.pdf},
}