@misc{indiciaee26b723d96c6,
  title = {Ring lens focusing and push-pull tracking scheme for optical disk systems},
  author = {Gerber, R. and Zambuto, J. and Erwin, J. K. and Mansuripur, M.},
  year = {1993},
  url = {https://ntrs.nasa.gov/citations/19940010517},
  note = {Source identifier: 19940010517}
}