@misc{indiciaeb373b28c32a1,
  title = {Gravitational lensing by a smoothly variable surface mass density},
  author = {Paczynski, Bohdan and Wambsganss, Joachim},
  year = {1989},
  url = {https://ntrs.nasa.gov/citations/19890042500},
  note = {Source identifier: 19890042500}
}